Final report small scale dab OFCOM (UK)

Small scale DAB trials Final report

Research report

Publication date: 26 September 2016

Small scale DAB trials: final report

About this document

During 2015, Ofcom licensed and co-ordinated a trial of a new approach to DAB radio broadcasting which we are calling small scale DAB. This document reports on the outcomes of the trial so far, particularly in relation to its three primary objectives, and sets out Ofcom’s conclusions. This document concludes Ofcom’s reporting to the Department of Culture, Media and Sport, who initiated and made funding available for the project.

Our report concludes that the trials were generally highly successful and achieved their three objectives. The trials showed that the small scale approach to DAB transmission is technically sound, and they helped Ofcom, the triallists, and wider industry to understand the practical requirements for successfully sustaining DAB radio transmissions using the small scale approach.

In light of stakeholder and wider interest in the technical aspects of the trials, we are also publishing several separate technical documents and studies as annexes alongside this report. The technical documents contain more in-depth information on the technical development and operational aspects of the small scale trials, as well as technical studies on potential frequency availability for small scale DAB, a technical report on DAB receiver performance that we commissioned during the project, and some summary results of a survey of radio stations on small scale DAB that we carried out while preparing this report. The technical documents are available on our website at http://stakeholders.ofcom.org.uk/market-data-research/other/radio-research/ssdab-final-report.

http://stakeholders.ofcom.org.uk/market-data-research/other/radio-research/ssdab-final-report



Contents

Section Page 1 Executive summary 1

2 Background to the trials 3

3 Implementing the trials 6

4 On-air technical experiences 13

5 Services, coordination and sustainability 18

6 Lessons for the wider market 22

7 Technical scope for wider roll-out 25

Annex Page 1 Predicted coverage maps for the small scale DAB trials 1


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Section 1

1 Executive summary 1.1 To date, many smaller analogue radio stations (broadcasting on FM or AM

frequencies) have been unable to transmit digitally on the DAB (Digital Audio Broadcasting) radio platform. This is usually due to the relatively high transmission costs that smaller stations would have to incur for carriage on existing DAB services. This, in turn, is often related to the fact that existing DAB services usually cover much larger geographical areas than smaller stations wish to serve.

1.2 A new approach to DAB transmission, known as ‘small scale DAB’, can potentially provide a more cost-effective way for these stations to broadcast on DAB. Small scale DAB keeps costs low by making use of relatively inexpensive transmission equipment and the freely available ‘open-source’ software maintained by Open Digital Radio1.

1.3 Small scale DAB can also achieve more ‘granular’ geographic coverage than existing DAB services, potentially making it more suited to smaller radio stations’ needs.

1.4 To help test the practical viability of small scale DAB, the Department for Culture, Media and Sport (DCMS) made funding available for real-world trials of the technology.

1.5 Ofcom awarded trial licences for ten towns and cities across the UK during 2015. Ofcom also provided assistance with technical development and support, and supplied transmission equipment to the triallists. The trial services were initially licensed for nine months.

1.6 The three main aims of the trial were:

• to test how well the small scale DAB technology worked;

• to test how well the technology lends itself to several parties coordinating their services (this is because DAB broadcasting involves several radio stations being transmitted as part of the same signal); and

• to give the market an opportunity to learn about small scale DAB and the potential opportunities the technology affords.

1.7 We have concluded that the trials successfully achieved all three aims:

• The technology generally worked well and reliably, and technical problems identified were resolved. We are continuing work to improve the technical stability of some specific transmitter configurations.

• Coordination between service providers has generally been very effective. Across the ten trial areas, nearly 70 unique radio stations are now being carried, the majority of which are new to DAB.

1 www.opendigitalradio.org, a non-profit organisation whose activities include maintaining open-source digital radio transmission software and tools.

http://www.opendigitalradio.org/


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• The ten trial operators have gained extensive practical experience of small scale DAB, and have also shared their experiences and technical knowledge with each other. Some operators have been directly involved in innovating further technical enhancements to the small scale concept, and the trials have prompted wider market interest.

1.8 As a result of the success of the trials, the current licences were extended for a further two years. The ten existing trial locations will remain on-air until 2018.

1.9 As part of this project, we have also looked at the availability of frequencies for small scale DAB. Our conclusion is that, when added to the spectrum available amongst the UK’s existing licensed DAB multiplexes, there is sufficient spectrum to support at least one small scale multiplex in most parts of the UK.

1.10 On the basis of the trials so far and the other conclusions of this report, we believe that there is a significant level of demand from smaller radio stations for small scale DAB, and that a wider roll-out of additional small scale services into more geographic areas would be both technically possible and commercially sustainable.


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Section 2

2 Background to the trials Radio in the UK

2.1 The UK has a large, diverse, and vibrant broadcast radio sector, which includes both the long-established FM and AM analogue radio platforms, as well as the newer Digital Audio Broadcasting (or DAB) digital radio platform.

2.2 DAB radio services are broadcast as ‘multiplexes’. This means that sound signals from a number of individual radio stations are combined together and transmitted as digital data. A DAB multiplex can be broadcast from many transmitters, all using the same transmission frequency, to cover a wide area. This is in contrast to analogue radio, where stations are simply broadcast on individual frequencies, and neighbouring transmitters cannot generally use the same frequencies as each other.

2.3 There are three ‘layers’ of commercial and independent radio in the UK: national radio stations, local radio stations, and community radio stations. In addition, the BBC provides its own national and local radio services.

2.4 On DAB, three national multiplexes (Digital One2, Sound Digital3, and the BBC’s national DAB service4) currently broadcast between 10 and 19 stations each. These national services are available to up to 97% of the UK population in the case of the most extensive network.

2.5 There are also 58 local commercial DAB multiplexes, covering approximately county-sized areas. Each local multiplex broadcasts up to 14 commercial radio stations, as well the relevant BBC local station for the area. Over 90% of UK households should be able to receive a local DAB multiplex by the end of 2016.

2.6 However, there are up to 400 local commercial and community radio stations on analogue radio which are not currently carried on DAB. This is partly because local DAB multiplexes cover relatively large geographical areas, which can make the cost of carriage uneconomic for stations which seek to serve smaller towns or communities.

2.7 In addition, some local DAB multiplexes are already full of existing stations, meaning that new stations can’t be added unless other services leave the multiplex or reduce the space they occupy (e.g. by moving from stereo to mono transmission).

Trialling an alternative approach: ‘small scale’ DAB

2.8 In 2012 and 2013, Ofcom engineer Rashid Mustapha carried out an initial trial in Brighton to test a new technical approach to DAB transmission. This trial took advantage of inexpensive computers, open-source software released by the Communications Research Centre in Canada, and a relatively novel ‘software defined radio’ module, to replace many of the dedicated hardware components used in traditional DAB transmission systems with lower cost alternatives. These initial

2 http://www.ukdigitalradio.com/ 3 http://www.sounddigital.co.uk/ 4 http://www.bbc.co.uk/reception/radio/digitalradio/

http://www.ukdigitalradio.com/

http://www.sounddigital.co.uk/

http://www.bbc.co.uk/reception/radio/digitalradio/


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trials showed that the new approach had the potential to significantly reduce the capital and operating costs of DAB broadcasting for smaller multiplexes.

2.9 The full report of this trial is available on the Ofcom website5.

2.10 Following the success of the Brighton trial, the Department for Culture, Media & Sport (DCMS) asked Ofcom to further develop the small scale concept, and to carry out a series of ‘real world’ trials of the small scale DAB system. The DCMS also made funding available to support the trials.

The role of stakeholders in the trials

2.11 A key element in delivering this project was for radio stakeholders to be deeply engaged in trialling the small scale approach to DAB transmission. This was in order to test the longer-term reliability, capabilities, and viability of the platform when deployed in a real-world context by broadcasters.

2.12 The Brighton trial was very limited in its duration and focus, as it used only one transmitter and carried no radio stations (due to restrictions which prevent purely technical trials from carrying broadcast content). We felt that it was important to test the approach more widely, from both a technical and an implementation perspective. We also concluded that it was crucial to include as wide a range of stakeholders as possible, and to include transmissions of ‘real’ radio stations, in order to further develop and validate the small scale approach.

How we proposed to carry out the trials

2.13 In October 2014 Ofcom began a consultation on proposals for three trial small scale DAB multiplexes, which would be run by radio sector stakeholders. We anticipated awarding trial licences for one of each of the following trial scenarios:

• Trial Type 1: a single transmitter multiplex carrying multiple services;

• Trial Type 2: a Single Frequency Network (SFN) carrying multiple services from two transmitter sites; and

• Trial Type 3: an SFN carrying multiple services based on two transmitter sites, with one of them being an ‘on-channel repeater’6.

2.14 Following this consultation, in February 2015 we published a statement confirming the three primary objectives of the trials:

• to test the function, capability and stability of software-defined DAB multiplex technology, particularly in SFN mode;

5 http://stakeholders.ofcom.org.uk/binaries/research/radio-research/Software-DAB-Research.pdf 6 A DAB on-channel repeater consists of a transmitter which picks up a signal directly from another DAB transmitter, and then re-transmits it. This basic principle has been used for many decades by TV and radio ‘relay’ transmitters (which transmit on a different frequency to the incoming signal). However, because an on-channel repeater transmits on the same frequency as the incoming signal, relatively complex electronic signal processing is required (and special attention must be paid to the aerial systems) in order to make the system stable and to avoid causing interference.

http://stakeholders.ofcom.org.uk/binaries/research/radio-research/Software-DAB-Research.pdf


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• to test how well the available technology lends itself to several parties coordinating their services into the multiplex (many small scale radio services do not have experience of using multiplexing technology); and

• to give the market an opportunity to learn about the software-defined DAB platform and the potential opportunities the technology affords, particularly for those stakeholders who are not familiar with digital broadcasting.

2.15 Following high levels of demand from radio stations and other stakeholders to take part, we also increased the number of trials available from three to ten. We stated that we would seek to award one licence for trial type 3 (the on-channel repeater), two for trial type 2 (the SFN), and the remaining seven for trial type 1 (the single transmitter trials).

2.16 At the same time as this statement, we published an Invitation to Apply for trial multiplex licences.

2.17 A full set of documents about the trial consultation process can be found on the Ofcom website at http://stakeholders.ofcom.org.uk/consultations/small-scale-dab/.

http://stakeholders.ofcom.org.uk/consultations/small-scale-dab/


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Section 3

3 Implementing the trials 3.1 Although the trial multiplexes are operated independently by stakeholders, Ofcom

played an active role in their development, particularly in the early stages. This section outlines Ofcom’s involvement in the trials in terms of licensing, construction and supply of transmission equipment, compiling and configuring software modules, and technical support.

Licensing

3.2 In response to our February 2015 Invitation to Apply for trial multiplex licences, Ofcom received 51 applications for the ten available licences. The majority of these were for the single transmitter trial type. We also received ten applications for the SFN trial, and three for the on-channel repeater trial.

3.3 In June 2015 we announced the award of the ten licences. The table below shows the successful trial licensees:

Trial type Licensee Location

Trial type 1 (single transmitter trial)

Angel Radio Portsmouth BFBS Aldershot Woking7 Brighton & Hove Radio Brighton Celador Radio Bristol Future Digital Norfolk Norwich Niocast Digital Manchester Switch Radio Birmingham

Trial type 2 (SFN trial)

Scrimshaws Information Directories Glasgow U.DAB London

Trial type 3 (on-channel repeater) UKRD Cambridge

3.4 All ten successful trial licensees proposed to carry at least four radio stations, including a mix of commercial and community stations, and had access to transmitter sites that appeared to be suitable for serving the areas that they had proposed.

3.5 The full account of the award decisions, including a list of the stations that the successful trial applicants proposed to carry, is available at http://licensing.ofcom.org.uk/binaries/radio/digital/small-scale-trial-multiplex-licensing/trial_awards_statement.pdf.

3.6 Following licence award, Ofcom worked to procure, supply and integrate certain elements of the transmission chain which met each licensee’s specific requirements,

7 The Woking trial was originally intended to serve Aldershot. however due to transmitter site acquisition issues, a site serving Woking was eventually used.

http://licensing.ofcom.org.uk/binaries/radio/digital/small-scale-trial-multiplex-licensing/trial_awards_statement.pdf

http://licensing.ofcom.org.uk/binaries/radio/digital/small-scale-trial-multiplex-licensing/trial_awards_statement.pdf


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and we held training sessions to familiarise licensees with configuring and operating their equipment.

3.7 The first trial multiplex came on-air during July 2015 in Brighton, with other services coming on-air through the summer of 2015. The final service to launch was in Glasgow, which went live in November 2015.

Equipment

3.8 Ofcom procured and provided each triallist with a largely standardised set of transmission equipment, which comprised the following main components:

• Up to six audio source encoders (comprised of single board computers and low-cost USB sound devices);

• A multiplexer (a small form factor desktop PC);

• A modulator (a ‘software defined radio’ peripheral);

• A linear VHF power amplifier;

• A 250 watt mask filter;

• A transmitting antenna and feeder cable;

• Other miscellaneous equipment including a network switch and an uninterruptable power supply (suitable for supporting all the electronic equipment apart from the power amplifier).

3.9 For trial type 2 (the SFNs), precision timing reference boards were added to the software defined radio modules to allow synchronisation of the transmitters within the SFN.

3.10 For trial type 3 (the on-channel repeater), a dedicated on-channel repeater unit (integrated by the manufacturer within the same chassis as a VHF power amplifier) was provided in place of one of the standard power amplifiers.

3.11 Although we sought to standardise the equipment provided to each triallist where possible, we introduced variations in some specific equipment types in order to reduce the risk of batch faults, and to provide a ‘mix’ of equipment for comparative evaluation during the trial. For example, we sourced power amplifiers from two separate manufacturers, and eventually deployed three models of single-board computer for the audio encoders.

3.12 Different transmitting antennas were selected based on the proposed transmission site and desired coverage. Omnidirectional antennas were used in most cases, while directional antennas were used in a few cases.

3.13 For multiplexer and modulator components, it was important to for us to supply standardised hardware and software platforms to enable on-going development and optimisation of these components during the trial. Therefore, the equipment used for these tasks – the software defined radio and desktop PC - were the same for all trials.


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3.14 The approximate average cost (including VAT) of the equipment provided by Ofcom was:

• £9,000 for trial type 1 (single transmitter);

• £17,000 for trial type 2 (SFN), comprised of one set of transmitter equipment for each of the two transmitter sites within each SFN; and

• £19,000 for the type 3 (on-channel repeater) trial. As with the type 2 trials, two sets of transmitter equipment were required, of which one set included the specialised on-channel repeater unit.

3.15 Ofcom also offered to meet the costs of the internet circuits required to provide links between multiplexing sites and transmitters, and offered to provide limited support for audio contribution links (e.g. between radio station studios and the multiplexing site). Five triallists opted to use such circuits, with the remaining triallists either using existing connectivity or procuring their own circuits.

3.16 There was a relatively wide variation in the costs of the internet circuits funded by Ofcom. The circuits selected varied from standard business-grade ADSL broadband and VDSL fibre broadband (supporting single transmitter trials), to Ethernet over Fibre To The Cabinet (EoFTTC) circuits which were used in one of the SFN trials.

3.17 Licensees were responsible for meeting the cost of equipment installation, including the installation of their transmitting antennas. Licensees were also responsible for providing connectivity (usually fixed broadband circuits) where these were not funded by Ofcom.

3.18 A more detailed technical description of the equipment used in the trials is provided in Annex 28, and the photographs below show the main transmitter system components supplied by Ofcom.

8 Annex 2, http://stakeholders.ofcom.org.uk/market-data-research/other/radio-research/ssdab-final-report




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Figure 1: Trial transmitter equipment – main components

Technical support

3.19 The multiplexer and audio encoder systems provided to each triallist were developed, configured, and tested by Ofcom and ran standard software. The multiplexers used ODR-DabMux9 software running on the Debian GNU/Linux operating system, and

9 https://github.com/Opendigitalradio/ODR-DabMux

VHF power amplifier (model 1)

Desktop computer (multiplexer)

Software defined radio peripheral

Managed Ethernet switch

VHF power amplifier (model 2)

Uninterruptible power supply

Single board computer (audio source encoder)

250 watt mask filter

https://github.com/Opendigitalradio/ODR-DabMux


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the source encoders used toolame-dab10 running on the Ubuntu GNU/Linux operating system (tailored for the specific single board computer systems used).

3.20 Ofcom provided training to all triallists to help familiarise them with the operation of the equipment. During the training we helped the triallists to carry out basic configuration of their systems to suit their specific needs (e.g. configuring the multiplexer to receive the desired audio services, and to set appropriate transmission parameters).

3.21 Ofcom also provided technical support to the triallists throughout the duration of the initial nine month trial. We have now scaled back our technical support role, partly because the initial trial period has now elapsed, and partly because licensees are now more familiar with the operational aspects of their equipment. However, we are continuing to provide support on a ‘reasonable endeavours’ basis for urgent issues, and are continuing our collaboration with the wider Open Digital Radio project to help refine the performance of the software.

Commissioning, Adjacent Channel Interference and coverage checks

3.22 All new radio transmitter sites go through a process of engineering checks known as ‘commissioning’. The main aims of this process are to ensure that the transmitted signal does not exceed the maximum power level set out in the broadcaster’s licence, and that limits to the level of signals generated outside of the frequency ‘block’ allocated to the DAB multiplex are being properly met. This is in order to ensure that neighbouring frequency spectrum users do not suffer undue interference. Ofcom carried out commissioning of all the small scale transmitter sites, and provided support and advice on system optimisation during the commissioning process where needed.

3.23 Another important part of the commissioning process was to ensure that the small scale DAB transmitters were not causing ‘ACI’ (Adjacent Channel Interference) issues. ACI is an effect that can sometimes be caused when a new DAB transmitter comes into operation, and occurs when relatively high signal strengths in the immediate vicinity of the new transmitter can effectively ‘block’ listeners’ reception of weaker signals from more distant DAB transmitters. The modest power levels used for the small scale DAB transmitters (along with careful selection of transmitting aerials) helped to avoid these problems, and no significant ACI issues were encountered during the trial.

3.24 Existing local and national multiplex operators are responsible for liaising with other multiplex operators in the areas where new transmitters are proposed in order to minimise possible ACI effects. Where required, this allows the parties involved to negotiate directly as well as enabling Ofcom to arbitrate if necessary. In the case of the small scale DAB trials, Ofcom carried out this liaison itself so that services could come on-air quickly. For any small scale DAB enhancement transmitters, or in any future permanent licensing regime, Ofcom would expect small scale multiplex operators to seek such agreements themselves. More detailed information on the commissioning and ACI aspects of the trials is available in Annex 211

10 https://github.com/Opendigitalradio/toolame-dab 11 Annex 2, http://stakeholders.ofcom.org.uk/market-data-research/other/radio-research/ssdab-final-report

https://github.com/Opendigitalradio/toolame-dab




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3.25 Ofcom also carried out computer modelling to predict the coverage area that each small scale transmitter was likely to achieve (see Annex 1). We validated these predictions by carrying out vehicle-based measurements of the coverage that each small scale transmitter actually achieved in practice. We found a close correlation in most cases, and where there was a significant mis-match, this was found to be due to issues with the transmitting antennas.

DAB receiver testing

3.26 Because many of the small scale trials used transmission frequencies which had not previously been used for DAB services in the UK, staff from Ofcom’s spectrum engineering team carried out some initial technical testing of a range of domestic and in-car DAB receivers to ensure that the receivers would operate as expected on the new frequencies. We also carried out basic sensitivity tests on receivers operating on the new frequencies. No significant functional issues were found during this testing.

3.27 We also subsequently commissioned a more detailed study of receiver sensitivity from DTG Testing Limited12 which is available as Annex 613 to this report. This found that while all the receivers tested could tune to the new frequencies, the sensitivity of individual models of DAB set varied considerably (on both the new frequencies and on existing DAB frequencies). This finding was consistent with our previous in-house basic sensitivity testing.

3.28 In general, receiver sensitivity has been improved considerably over time, and newer sets tend to provide the most reliable reception experience. This highlights the importance of the Digital Tick scheme14. Manufacturers must prove that their products meet (or exceed) a minimum performance specification before the Tick mark can be displayed on packaging and marketing materials for the radio set.

Reporting

3.29 Alongside providing equipment, support and commissioning, Ofcom required triallists to provide weekly reports on progress against their launch plans during the pre-launch period. This proved helpful in understanding the issues triallists were facing as they arose.

3.30 After launch, triallists had to report on a fortnightly basis, and keep a reporting log for submission to Ofcom every month. This was to ensure that all relevant information was being captured.

3.31 Triallists have now moved to reporting monthly, and will continue to do so until the end of their trial licence, so that Ofcom can continue to gather information on the long-term stability of the small scale approach, and on how the market is developing.

12 DTG Testing (www.dtgtesting.com) is a UKAS accredited test facility whose services include testing DAB radios for compliance with the ‘digital tick’. DTG Testing also carries out performance and functional testing of digital television equipment. 13 Annex 6, http://stakeholders.ofcom.org.uk/market-data-research/other/radio-research/ssdab-final-report 14 www.getdigitalradio.com/industry/what-is-the-tick-mark, a scheme which allows radio receivers meeting specified minimum performance standards to display the ‘digital tick’ certification mark.

http://www.dtgtesting.com/



http://www.getdigitalradio.com/industry/what-is-the-tick-mark


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3.32 We also invited the trial multiplex operators and stations on small scale DAB to complete internet surveys during August 2016. This was primarily in order to gain further insights into their experiences of small scale DAB for this report

3.33 The reporting we have received, as well as the survey results, have contributed to this report, which also draws on Ofcom’s own observations and analysis. We are grateful for the useful information we have received from triallists over the course of the trials.


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Section 4

4 On-air technical experiences Background

4.1 The main technical objective of the trials was to test the function, capability and stability of software defined DAB multiplex services, particularly in single frequency network (SFN) mode.

4.2 The small scale DAB approach has never been trialled over an extended period in the UK, nor in so many trial areas, and we wanted to test whether it could perform reliably in a range of circumstances. At the start of the trial, it was also unknown whether the small scale approach would operate reliably in SFN configuration.

4.3 In the ten trials, we planned at the outset to award licences for seven single transmitter multiplexes, two two-site single frequency network multiplexes, and one two-site multiplex using an on-channel repeater.

4.4 The on-channel repeater trial took place in Cambridge, while a two-site SFN trial took place in London. As of August 2016, two trials are in the process of adding second transmitters, effectively turning these multiplexes into SFNs. The Glasgow trial was originally intended as a two-site SFN, but the operator experienced delays in bringing the second site into operation, and the SFN did not become fully operational until May 2016.

4.5 This section provides a high-level summary of the technical approach to the trials, and the lessons we learnt. A more detailed account of the trials’ technical architecture, performance, and issues encountered is available in Annex 215.

Hardware

4.6 The trial transmission hardware generally worked well and proved extremely reliable. The most significant issues encountered were related to hardware failures rather than the small scale architecture itself.

Software

4.7 The multiplexing and audio encoding software proved highly reliable during the course of the trials for most operators. Some single-transmitter trial operators reported occasional instances where equipment needed to be restarted, but these were generally restricted to early stages of the trial, and no definitive cause was identified. In other trials, the software operated reliably throughout and required no user intervention except to implement service reconfigurations (such as adding new stations to the multiplex).

4.8 The most significant software issue was a problem related to the synchronisation of the transmitters in the SFN trials. Transmitters in an SFN need to be precisely synchronised together so as not to cause interference to each another, and to provide the coverage enhancing effect which is one of the main advantages of DAB





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operating in SFN mode. However, we found that the trial SFN transmitters would periodically experience timing issues, and the modulators needed to be reset by remote control to clear the problem. We carried out extensive technical investigations to understand and rectify this issue.

4.9 We believe that the root cause of the problem has been identified, and as the timing problem appears to have been resolved we will be issuing updated software to the two SFN triallists during September 2016.

4.10 The main focus of our technical development work on the trials was to provide core software and equipment functionality to enable the trials to go ahead. Therefore ‘ease of use’ issues were not a primary objective, and we did not provide graphical or web interfaces for the multiplexing or encoding software. Configuring the equipment therefore required relatively advanced IT skills. While the majority of the triallists’ organisations included suitably skilled engineers or technical staff (and Ofcom was able to offer support in other cases), any wider roll-out of small scale DAB would benefit from more user-friendly configuration, operational, and monitoring tools being available. The software development community and market are now beginning to deliver these.

Single transmitter trials – Technical experiences

4.11 The coverage of the single transmitter trials closely matched our predictions, though we noted the following issues.

4.12 The coverage predicted and achieved by one of the single-transmitter trials was relatively limited. This was due to the use of a less than ideal transmitter site, and emphasises the need for good transmitter site selection.

4.13 During the course of the trial, one multiplex identified and moved to a better transmitter site and used a different aerial configuration. This improved coverage of their target area considerably.

4.14 One single transmitter trial initially had poorer coverage than expected towards the edge of its coverage area. We found that this was due to a fault with the transmitting antenna. The antenna was replaced, which significantly improved the coverage achieved within the target area.

4.15 One other single transmitter triallist reported that the coverage they were achieving fell short of their expectations, and received listener feedback to that effect. However, the coverage achieved was consistent with our coverage predictions. Serving a significantly wider area was not possible within the parameters of the single transmitter trial type.

4.16 The single transmitter trials generally proved very reliable in service. Some triallists initially experienced occasional reliability problems with the audio encoders, which were restricted to a single type of encoder computer. These encoders were replaced as required.

4.17 Licensees also generally found the equipment straightforward to use, but some degree of command line computer experience was necessary. At least two licensees developed their own web interfaces for controlling the multiplexer.

4.18 Some triallists indicated a wish to add an additional ‘enhancement’ transmitter site at their own expense. The enhancement sites are intended to improve building


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penetration and therefore to aid indoor reception, and in one case, to better serve the primary target area (as the original site was located some distance away). We will consider requests for additional transmitters on case-by-case basis, with a primary consideration being that new transmitters should not materially expand the overall coverage area of the multiplex.

4.19 The addition of enhancement transmitters involves updating software and the provision of GPS timing references and aerials. A feed between the multiplexer and the remote site is also needed, which can be a private data link or public internet connection.

4.20 Reception of the single transmitter trial multiplexes has been mostly in-line with the predicted coverage. Due to the temporary nature of the trials, operators tended to select transmitter sites to which they were able to gain easy access at low cost, rather than ones optimally placed to serve the target areas. Should small scale DAB services roll-out more widely, we expect that operators would be able to select more suitable sites.

4.21 The relatively low power levels used in the trials did also highlight that there is a large variation in sensitivity between different models of receiver: some reports of poor reception were from within areas which we had determined to be well-served through data collected from the driven field strength measurement campaigns. This variation in receiver sensitivity was also confirmed by the technical testing mentioned in sections 3.26 to 3.28.

Single frequency network (SFN) trials - Technical experiences

4.22 The coverage of one of the two SFN trials was broadly as predicted by computer modelling. However, the distance between the two trial transmitters was relatively large, and reception around the mid-point between the transmitters was more ‘marginal’ than expected: this area happened to fall into a densely built-up city centre, which is also likely to have contributed to the issue.

4.23 There was also evidence of reception blocking caused by other DAB transmitters, and a particular business radio system with many mobile stations. A moderate increase in transmitter power from 100W ERP to 200W ERP was implemented which improved the situation subjectively, though we believe that a significant increase in the reliability of reception is only likely to be achieved by adding a third transmitter (which would add cost) to the SFN, or by bringing the two existing transmitters closer together (which would have the side-effect of shrinking the overall coverage area). The use of DAB+ may also help to increase the area in which reliable in-building reception is possible due to its lower carrier-to-noise requirement, and because DAB+ sets are generally of more recent design (and therefore often provide better performance than older receivers).

4.24 The other SFN trial experienced several problems and protracted delays in establishing and maintaining their service, and was operating with only a single transmitter in non-SFN mode for several months. The transmitting antennas that were initially installed were found to be defective and were replaced. Availability of internet connectivity at one transmitter site was found to be of prohibitively high cost, resulting in a need to change site. Ongoing reliability problems have been experienced, which are likely to be due to poor internet connectivity. We do not believe these experiences are indicative of wider flaws with the small scale concept, but rather of issues specific to that trial multiplex.


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4.25 As mentioned above, achieving fully reliable synchronisation between the SFN transmitters has proved to be an ongoing issue, and has been a focal point of our continuing technical work over the duration of the trial. In service and in lab testing, the SFN transmitters would operate satisfactorily for some days or weeks, but would eventually lose synchronisation. The time-dependent nature of the effect made identifying the root cause particularly challenging, and various potential software and hardware issues were explored. We now believe we have identified an underlying software issue, and are in the process of issuing updated software builds to the two SFN triallists.

4.26 Again, licensees generally found the SFN transmitter equipment straightforward to use, but some degree of command line computer experience was necessary.

4.27 At the time of writing there is no working ‘Transmitter Identification Information’ (TII) functionality in the software. TII enables the signals from individual transmitters in an SFN to be monitored. Once TII has been implemented it will become much easier to monitor the stability of SFN operation.

On-channel repeater trial - Technical experiences

4.28 The Cambridge on-channel repeater trial used a primary transmitter site which was around 6km outside the city centre. The DAB signal from this site was picked up and re-transmitted by an on-channel repeater (OCR) which was located on a church within the city centre.

4.29 A process of iterative technical refinement and experimentation was required for the on-channel repeater to achieve stable operation, while also transmitting at a high enough power level to provide a useful enhancement to city-centre coverage. The receive aerial system originally planned for the repeater site needed to be replaced by a smaller type because of aesthetic concerns. The smaller aerial exhibited much lower gain than the originally-specified aerial, and could therefore only provide a proportionally lower level of signal to the on-channel repeater unit.

4.30 Achieving the required high level of radio frequency isolation between the transmit and receive aerials at the OCR site proved to be difficult due to the constraints of the building construction. The transmitting aerial was also found to have a defect which further reduced isolation between the two aerials. These aerials were replaced but the isolation achievable resulted in the repeater being operated at 50 watts ERP instead of the originally-intended 100 watts ERP. It is reasonable to expect that this restriction would be eased if aerials with characteristics closer to those originally specified could be used.

4.31 Although the planning of an on-channel repeater can be more complex, and the installation more demanding, than a standard transmitter, once installed they require very little attention. Repeaters do not require GPS references or broadband circuits associated with a conventional SFN. The higher unit cost of a repeater would also be offset by the cost savings of not requiring a broadband circuit to feed it.

4.32 The predicted coverage of the repeater station indicated that it would enhance reception in the north of the city. While a field strength survey indicated that the unit does indeed enhance the field strength within the city without causing any reception issues, the site operator does not believe the repeater provided any significant extension to the overall multiplex coverage area.


17

4.33 On-channel repeaters are a cost-effective and attractive solution for enhancing or extending coverage. However, as a function of their design, on-channel repeaters are best suited to situations where a directional transmitting pattern is desirable. They also require a good quality incoming signal from a favourable bearing, and can only be used where the sufficient radio frequency isolation between the receive and transmit aerial is achievable.

General technical experiences – DAB+

4.34 Reception reports and anecdotal evidence indicate that the use of DAB+, which was adopted by some triallists, has helped in providing satisfactory reception in some ‘fringe’ coverage areas where conventional (MPEG-1 Layer 2) DAB services in the same multiplex could not be decoded.


18

Section 5

5 Services, coordination and sustainability Background

5.1 The second main objective for the trials was to test how well the small scale DAB technology lends itself to several parties co-ordinating their services to form a multiplex, particularly when many participants will not have had experience of being carried on the DAB platform.

5.2 Unlike an analogue radio station, which is a single service carried on its own transmitter and frequency, a DAB multiplex consists of a number of stations which all share the same ‘pool’ of broadcasting capacity. They also share a common transmission infrastructure. The multiplex operator is responsible for managing the multiplex, including deciding which stations it should carry, and on what commercial terms.

5.3 Because Ofcom was not part of the commercial negotiations between the trial multiplex operators and radio stations, nor to any subsequent discussions between them, we have only a limited pool of direct evidence about the effectiveness of cooperation during the trial.

5.4 We have drawn on the regular multiplex operator reports that we received during the trial, as well as an overview of the evolving composition and status of the small scale DAB services.

5.5 We felt that it was important to gain some structured feedback directly from the radio stations involved in the trials. We therefore invited all current and former stations on small scale DAB multiplexes to complete an online survey which asked about their experiences, and their views on the future prospects for small scale DAB. Of the 69 stations invited to complete the survey, 40 did so, a response rate of 58%.

5.6 We also carried out a similar survey of trial multiplex operators. Nine out of the ten multiplex operators responded to the multiplex operator survey, a 90% response rate.

5.7 We are publishing a sub-set of the service providers’ survey responses as Annex 516. In order to preserve respondent confidentiality, we are not publishing survey responses which could be personally identifiable, or which may be commercially sensitive. Due to the small sample size and confidentiality issues, we are not publishing separate response summaries for the multiplex operator survey.

Limits on the ability of the trial to predict future behaviour

5.8 When considering the operators’ and stations’ experiences of co-operation during the small scale trial, we are mindful that the scale, nature, and duration of the trial means that it is unlikely to fully reflect the financial, commercial, and behavioural aspects of any future permanently-licensed services. There are several reasons for this.

5.9 Firstly, the bulk of the transmitter and ancillary equipment was provided to the triallists, meaning that start-up capital costs for the multiplexes were lower than they





19

would have been in an operator-funded situation. Telecoms circuit costs were also met by trial funding for some multiplexes.

5.10 The initial nine month trial licences were of a very short duration in comparison to conventional broadcast services.

5.11 For a variety of reasons, several multiplexes charged no, or minimal, carriage fees to the stations on their multiplexes. We also understand that most multiplexes did not agree contractual terms, such as standards of service availability and reliability, which normally form part of commercial radio carriage agreements.

5.12 For these reasons, some of the outcomes of the initial trial period must be viewed as indicative.

5.13 However, the behaviours and commercial relationships of the trial participants may well evolve over the remaining extended trial period to more closely match those that might be experienced in possible future permanent deployments. As part of our surveys, we therefore also asked multiplex operators and service providers about any changes they intend to make during the extended trial licence period.

Demand for small scale DAB from a range of different stations

5.14 The trials suggest there is a significant level of demand from potential multiplex operators and service providers for small-scale DAB.

5.15 We received 51 applications for ten trial multiplex licences. The trials indicated that there is likely to be a mix of operating models for multiplexes. Multiplexes were operated by existing commercial broadcasters, community radio services, and some non-broadcasting (multiplex only) operators.

5.16 At launch, the 10 trial multiplexes contained 72 stations, including 9 stations which were carried in more than one trial area.

5.17 The number of services rose over the course of the trial. By the end of the initial nine-month trial, 92 services (audio components) were being carried, of which 18 were services that were simulcast on more than one multiplex (and which were carried on between two and four multiplexes each).

5.18 Over the course of the initial nine month trial, four multiplexes had sufficient demand to adopt DAB+ for some services, and 27 DAB+ services are being carried (including some simulcasts) at the time of writing.

5.19 Several multiplexes, most notably Manchester and Portsmouth, saw a notable increase in the number of services carried during the trial, indicating a particularly strong demand from stations for an opportunity to join the DAB platform in these areas.

5.20 Of the 67 unique radio stations currently17 on small scale DAB, 12 are simulcasts of existing licensed commercial radio stations (meaning they are carried on either existing analogue or existing commercial DAB multiplexes), and 33 stations are new to terrestrial broadcast radio in the UK. The remaining 22 services are simulcasts of existing Ofcom-licensed analogue community radio services.

17 As of the end of August 2016


20

5.21 While there are fewer community radio simulcasts (22) than other services (45) currently on small scale DAB, a number of the ‘non-community’ services do have many of the characteristics of community radio, despite not holding an Ofcom Community Radio licence. For example, the 45 services include web broadcasters targeting specific communities, and ‘spin off’ or ‘time shift’ versions of existing licensed community radio stations.

Coordination and carriage charges

5.22 Overall, the coordination aspects of the trials appear to have worked positively. Multiplex operators and station operators generally worked efficiently together to establish the necessary agreements and technical arrangements for carriage of their services on the trial multiplexes. A majority of the service providers, 27 out of 37 respondents to our survey, claimed negotiating carriage on a multiplex was easy.

5.23 One objective factor which can help us to gauge the effectiveness of cooperation between service providers and multiplex holders is the terms (such as carriage fees) on which multiplexes carry services, and on service providers’ intentions for the future.

5.24 The trial multiplexes sometimes offered free carriage to services, as the multiplex was a relatively cheap means of additional distribution for their existing radio stations, not a core revenue stream. In other cases, stations on the multiplexes provided ‘in kind’ assistance (such as access to transmitter sites) to the multiplex operator in lieu of carriage fees. In other cases, the multiplex operator absorbed the running costs of the multiplex and did not charge carriage fees.

5.25 During the initial nine month trial, the nine multiplex operators who responded to our survey indicated that their primary approach to charging stations for carriage on the multiplex was either on a cost-recovery basis (five multiplexes) or that carriage fees were not generally charged (four multiplexes).

5.26 Service providers told us that, where carriage fees were being charged, the most common level of fees, for a third of the providers, during the initial trial period was between £200 and £499 per month.

5.27 For the reasons outlined above, the multiplex operators’ approach to charging for capacity during the initial trial period is unlikely to be extended to a wider or longer-term roll-out of small scale DAB. In our survey, all nine operators who responded have made, or plan to make, changes to the way they charge existing stations for carriage on their multiplexes during the remaining extended trial licence period. Four of the nine respondents have moved (or plan to move) to a more ‘commercial’ basis for carriage charges, with the remainder moving to - or planning to adopt - cost-recovery or other approaches.

5.28 Similarly, our survey of service providers indicated that while the majority (23 out of 27 respondents) expect carriage costs to remain the same or increase during the extended trial period, most service providers (27 out of 37 respondents) intend to remain on the small scale DAB platform. Where carriage fees are increasing, the survey responses indicate that, for half of the respondents, the most common level of increase in carriage fees per service is between £51 and £100 per month.


21

Views on the commercial sustainability of future small scale DAB services

5.29 We asked the multiplex operators and service providers whether they felt that a wider roll-out of small scale services would be financially sustainable.

5.30 The majority of multiplex operators (5 of the 8 respondents who answered this question) said they felt that small scale DAB would be commercially sustainable for new entrant multiplexes even where the multiplex operator was responsible for covering all equipment costs as well as running costs. The remainder answered “don’t know”.

5.31 21 respondents out of 37 service providers who answered a similar question felt that a wider roll-out of small scale DAB would offer a commercially sustainable method of distribution for their service, with 11 answering “don’t know”, and 5 answering “no”.

5.32 A relatively higher number of Community Radio service providers felt that small scale DAB would provide a commercially sustainable distribution method for their service: 8 out of the 10 Community Radio services who answered this question did so positively. Service providers noted that the relatively lower costs of carriage compared to other DAB platforms was important to this.

5.33 From follow-up questions, we noted that the uncertainty of “don’t know” respondents primarily stemmed from issues such as concerns around reported shortfalls in the coverage and reception experienced compared to that predicted, to other issues unrelated to the trial itself e.g. lack of audience impact (and corresponding difficulties in measuring their DAB audiences), and the level of licence fees required for playing recorded music.

5.34 Those service providers who felt that small scale DAB would not offer a viable platform for them also cited concerns that the size of their coverage area was too small, and of ‘patchy’ reception (on one of the single transmitter trials). Another service provider cited poor reliability of the transmitter (on one of the SFN trials).

5.35 The survey results, along with our previous feedback from small scale DAB providers, suggest there is also a high level of uncertainty about the carriage fees that might be charged in any permanent multiplex deployment. Multiplex operators have told us that it is very difficult to predict the level of fees as much will depend on factors such as the business model of the multiplex operator, the technical architecture of the service, and the location of the multiplex.

5.36 We expect that multiplex operators in any permanent deployment would be innovative when designing their services – for example, ‘single ended’ transmission systems (i.e. systems with little or no backup equipment in case of equipment failure) may well be acceptable in some circumstances - and therefore the carriage costs may vary between multiplexes.

5.37 While we note these uncertainties, we believe it is credible that carriage costs on small scale DAB might be, at most, comparable to FM transmission costs for most services. Furthermore, depending on the multiplex business model, and possible use of transmission modes which demand less capacity (e.g. DAB+), it could be possible for ‘real world’ costs to be significantly less than for FM.


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Section 6

6 Lessons for the wider market Background

6.1 Our third key objective for the trials was to give the market an opportunity to learn about the software defined approach to DAB and its opportunities, particularly for those stakeholders not familiar with DAB broadcasting.

6.2 The main Ofcom-licensed trials were operated by 10 different companies, ranging from existing commercial and community radio broadcasters to ‘new entrant’ providers, giving groups from a wide range of backgrounds the opportunity to gain valuable experience of operating a DAB multiplex.

6.3 The trials also provided an opportunity for over 70 community and commercial radio stations to join one or more trial multiplexes: the majority of these services have never been broadcast on DAB before.

Innovations during the trials

6.4 While Ofcom designed the trial transmitter systems to transmit standard DAB services, we left the option open for triallists to adopt the newer DAB+ audio encoding standard, subject to them obtaining suitable technology licensing rights. Some triallists did subsequently adopt DAB+, which allowed additional services to be carried on their multiplexes. Further information on the DAB+ services and their role in the trials is available in Annex 218.

6.5 Some trial operators supported each other on technical matters and common issues by communicating through an online forum. They also set up a software repository to share software developments specific to the UK trials. Others have also joined the Google group ‘mmbtools’19 which is the official user forum operated by Open Digital Radio.

6.6 Some triallists implemented DAB ‘Slideshow’ transmissions on their multiplexes. This allows compatible receivers to display multimedia objects such as programme-related graphics, weather forecasts, or track information.

6.7 One triallist implemented an Electronic Programme Guide (EPG). This allows compatible receivers to display information about upcoming programmes on the multiplex.

6.8 In addition to the main ten trial multiplexes, an independent multiplex began operating while the trial was taking place, with interest having been stimulated by the trials. This service used similar techniques and equipment to the main small scale trials, and was self-funded by the operator. This multiplex was licensed under a non-operational ‘test and development’ Wireless Telegraphy Act licence (as the original 2012/13 Brighton trial had been). This meant that it could only transmit test audio

18 Annex 2, http://stakeholders.ofcom.org.uk/market-data-research/other/radio-research/ssdab-final-report 19 https://groups.google.com/forum/#!forum/crc-mmbtools



https://groups.google.com/forum/#!forum/crc-mmbtools


23

rather than radio programming. Ofcom is also aware that several other users have been testing self-built systems under suppressed radiation conditions.

6.9 Ofcom staff have followed these developments and we noted the enthusiasm and resourcefulness of the operators in successfully applying small scale techniques outside the main trial.

Equipment commercialisation and software enhancements

6.10 To date, small scale DAB transmission hardware has not been extensively commercially integrated or marketed, but this is already under way as the open-source nature of the software enables products to be rapidly developed to complement the pre-existing software building blocks (providing that the code base is used in accordance with the GNU General Public Licence). Those who are experimenting with the technology have integrated their own systems from commodity or general purpose equipment (as we have done in the UK). If a permanent licensing framework were to be established in the UK and/or in other countries, more equipment vendors may well begin to offer pre-built systems that are easier to set-up and configure than the current tools.

6.11 As mentioned in section 4.10, it is possible for the core open-source software used in small scale DAB to be supplemented by additional open-source ‘front end’ configuration tools and interfaces. This has already happened, albeit to a limited extent, in the UK trials.

International market developments

6.12 Permanent radio services based on the software defined approach used in the UK’s small scale trials are already on-air in Switzerland and France, with trials taking place in a growing number of European countries. Other regulators in Europe have approached Ofcom to express their interest in the small scale approach, and to find out more about our trials.

6.13 This suggests there are potentially opportunities for small scale DAB to be deployed in several more countries, which may for example stimulate integration and commercialisation of software-defined DAB hardware.

Triallists

6.14 As mentioned earlier in this report, the triallists come from a wide range of backgrounds. Several trial groups included experienced broadcast industry engineers as part of their teams. Some groups were able to call on such expertise for some or all of the tasks required when setting up and running their multiplexes. Others were less well-resourced.

6.15 Groups with specialists on-hand required less technical support from Ofcom than groups with less broadcast engineering experience or skills. We believe however that all triallists gained valuable knowledge and experience of small scale systems.

Wider industry awareness

6.16 The small scale DAB trials have provoked a significant amount of interest in the concept from both industry and the public.


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6.17 The trials have been recognised by industry to be an incubator for both innovative broadcast radio services and digital radio technology. The first regular service to use DAB+ in the UK was by a small scale trial, and some trial multiplexes already carry rich multimedia content including logos, slideshow and EPG which can be displayed by some newer receivers such as car infotainment systems, and a growing number of handheld and portable receivers.


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Section 7

7 Technical scope for wider roll-out Introduction

7.1 One of the key technical requirements for any future wider roll-out of small scale DAB services is the availability of sufficient transmission frequencies to enable a range of multiplexes to launch, and to enable the multiplexes to achieve desired levels of coverage.

7.2 This section sets out the main conclusions of technical work and studies that Ofcom has carried out which look at frequency availability for small scale DAB. We first considered the frequencies needed to support the small scale trials themselves, and then carried out a theoretical study looking at the potential availability of frequencies for any future small scale DAB roll-out. A summary of these studies is available as Annex 3 to this document, and the main technical study itself is available as Annex 420. Please note that this work is purely indicative, and was solely intended to assist with assessing the potential for wider deployment of small scale DAB. Further technical planning work would be required in order to develop a detailed practical frequency plan.

Frequencies used in the small scale trials

7.3 DAB transmitters in the UK currently use VHF (Band III) frequency ‘blocks’ which range from approximately 211 MHz to 229 MHz (known as blocks 10 to 13). These frequencies provide sufficient spectrum to support three national DAB multiplexes and the current 58 local commercial DAB multiplexes.

7.4 However, when we initially looked at the prospects for the small scale DAB trials, it was clear that additional spectrum would be required. Because DAB radio receivers can also tune into lower frequencies than those currently used in the UK, we examined the availability of frequencies below 211 MHz for use during the trials.

7.5 Much of this part of the VHF frequency band has until recently been used by private business radio services in the UK. However, as part of international re-planning of frequency use, business radio users on some of these lower frequencies have generally migrated their services to other frequencies.

7.6 This provided an opportunity for additional spectrum to be used for the small scale DAB trials in a part of the VHF band known as ‘sub-band II’ (blocks 7, 8 and 9). Careful frequency planning was still required in order to avoid interference with the remaining business radio users in the band, and some frequencies needed to be avoided altogether.

7.7 Eight of the small scale trial multiplexes therefore shared two of the sub-band II frequencies (on approximately 194 MHz and 203 MHz – or block 7D and block 9A). The remaining two small scale DAB trials used existing DAB frequencies on an ‘interleaved’ basis where those frequencies were not used by other DAB multiplexes.

20 Annexes 3 & 4, http://stakeholders.ofcom.org.uk/market-data-research/other/radio-research/ssdab-final-report




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Future frequency availability

7.8 The remaining business radio users in sub-band II will be migrating to other frequencies over the next few years. This will potentially make six sub-band II frequencies available for DAB use across much of the UK in future. The frequencies comprise blocks 7D, 8A, 8B, 9A, 9B and 9C.

7.9 While the migration of business radio will remove many of the current constraints on the use of these frequencies for any future small scale DAB services, some neighbouring countries also have established international rights to use these frequencies. This may limit the extent to which the sub-band II frequencies could be used in some areas of the UK.

7.10 However, initial indications are that the six sub-band II frequency ‘blocks’ would be sufficient to enable the deployment of small scale DAB across much of the UK. Where required and feasible, unused ‘gaps’ in the existing DAB frequency allocations could also be used on an interleaved basis (as they were in the trial).

DAB frequencies that might accommodate existing analogue radio services

7.11 We also carried out an initial study looking at whether it would be technically feasible to develop a future frequency plan for small scale DAB that might provide an opportunity for those small commercial and community stations currently transmitting on analogue radio only to be carried on DAB.

7.12 We concluded that in most areas of the UK, it should be technically possible to develop a frequency plan for small scale DAB which might accommodate those stations. However much more detailed planning and optimisation work would be required to develop a frequency plan which could be implemented in practice.

7.13 Because the UK’s neighbours have established rights to use the sub-band II frequencies (and some are already doing so), we would also need to negotiate the use of these frequencies for small scale DAB with neighbouring countries.

7.14 As mentioned above, another important (though temporary) technical constraint is that in some areas of the UK business radio services are currently using part of the VHF band identified for possible future use by small scale DAB. Our study indicates that this is likely to cause a shortage of frequencies until the business radio services migrate to other frequencies (which is due to happen by 2020). The areas most likely to be affected by these interim restrictions are north Somerset & south east Wales, the East Midlands, and areas to the south of Manchester.


1

Annex 1

1 Predicted coverage maps for the small scale DAB trials A1.1 The maps below show coverage predictions for the small scale DAB trial multiplexes. The predictions were produced using the ATDI

ICS telecom radio propagation modelling tool, and were validated with drive measurements.

A1.2 The wanted DAB coverage predictions for individual transmitters were carried out using our standard Fresnel / Deygout propagation model and Infoterra clutter model for 99% mobile locations and 80% indoor locations.

A1.3 Outdoor mobile coverage has been based on a minimum field strength of 54dBuV/m, and indoor portable coverage has been based upon a minimum field strength of 63dBuV/m.

A1.4 For the SFN and on-channel repeater trials (London, Glasgow and Cambridge) any overlapping coverage is power summed, giving an overall increase in field strength within the overlapping coverage area.

A1.5 Ofcom and the broadcasters normally carry out DAB coverage planning using the UK Planning Model (UKPM) prediction software. Predicted coverage maps for the small scale DAB trials using UKPM are available on our website at http://licensing.ofcom.org.uk/radio-broadcast-licensing/digital-radio/mux-licensing/small-scale-trial-multiplex-licensing/coverage/, and these will be kept up-to-date with any future transmitter changes.

A1.6 Coverage maps produced in UKPM do differ from those produced in ICS telecom below. However, it is not possible to correlate UKPM maps with drive measurement data, therefore ICS telecom maps are provided here for reference.

http://licensing.ofcom.org.uk/radio-broadcast-licensing/digital-radio/mux-licensing/small-scale-trial-multiplex-licensing/coverage/


2

Figure A1: Birmingham


3

Figure A2: Brighton


4

Figure A3: Bristol


5

Figure A4: Cambridge


6

Figure A5: Glasgow


7

Figure A6: London


8

Figure A7: Manchester


9

Figure A8: Norwich


10

Figure A9: Portsmouth


11

Figure A10: Woking

Small scale DAB: Frequency planning feasibility study

Technical study: August 2015

Published with minor editorial amendments as Annex 4 to the small scale DAB trials final report: 26 September 2016

Small Scale DAB: Frequency planning feasibility study

Summary Ofcom is publishing this study to accompany our final report to Government on the small scale DAB trials. The technical work for this study was carried out during the second half of 2015, and the content of this document reflects the situation at that time.

Spectrum requirements for small scale DAB

To increase the opportunities for community radio and small scale analogue commercial radio services to join the DAB digital radio platform, ‘small scale DAB’ multiplexes are being considered.

UK DAB services are currently provided using spectrum within a part of VHF band III known as ‘sub-band III’1. An initial study, carried out for the Manchester area, concluded that further spectrum beyond that available in sub-band III would be required to provide small scale multiplexes in any future wider roll-out of small scale DAB.

What we did

This study considers the technical feasibility of such a wider roll-out from a frequency availability and frequency planning perspective. The study contains details of a theoretical small scale DAB network which has been developed solely to assist with producing this feasibility study. These ‘notional’ networks are purely indicative, and more detailed frequency planning, international engagement and internal UK coordination work would be required before practical networks could be deployed.

We have identified six frequency blocks from another portion of VHF Band III, known as ‘sub-band II’2 that could potentially be used for small scale DAB. Sub-band II was previously allocated to business radio (or Private Mobile Radio - PMR) services. PMR has largely vacated this spectrum as a result of changes to international frequency plans following the ITU Regional Radio Conference held in Geneva in 2006, but some PMR services may remain in the sub-band until 2020.

Conclusions

Using this additional spectrum, we have developed a notional frequency plan for 192 small scale DAB multiplexes. Notional multiplexes have been formed from a selection of the transmitter sites that are currently used to provide existing community and small analogue commercial radio services.

As small scale DAB services are expected to operate at relatively low power levels, it will be necessary for their transmitter sites to be near to the target coverage area in order to provide robust ‘indoor’ coverage to urban areas. Existing community and small scale sites were not always found to be satisfactory.

1 210.8 MHz to 230 MHz (DAB blocks 10B to 12D) 2 193.2 MHz to 207.5 MHz (DAB blocks 7D to 9C)


The UK ‘mobile’ coverage achieved by the notional sub-band II plan developed in this study is shown in figure 1.1

Figure 1.1 UK small scale DAB ‘mobile’ coverage, using six sub-band II blocks

7D

9B

8A

9A

8B

9C

Map Images © Copyright. All rights reserved Ofcom Licence No 100018047 - 2015


We have found that in some areas, additional spectrum resource (beyond the six sub-band II frequency blocks) is likely to be required in order to avoid undue interference between the notional small scale DAB multiplexes. Therefore, we have also considered the use of sub-band III blocks (where these are available) to supplement the six sub band II blocks in areas of limited frequency availability.

We have concluded that small scale DAB multiplexes could be interleaved with local DAB services, although only one or two interleaved blocks may be available in each region. These blocks may assist where more than six blocks are needed, or where continental interference is problematic. However sufficient sub-band III spectrum would not available for mitigation against the interim PMR constraints (where these exist) in several areas.

Constraints

PMR services may continue to make use of sub-band II spectrum until 2020 in south Yorkshire, the east midlands, and in Merseyside. This is likely to prevent the comprehensive roll out of small scale DAB within the north of England, the English Midlands, the northern Home Counties and the north west of England in the short term. Analysis of the co-existence of PMR with the notional small scale DAB frequency plan developed during this study indicates that 59 of the 192 Small Scale DAB multiplexes would not be able to launch until PMR migrates from sub-band II.

In border or coastal regions, the plan has avoided frequency blocks planned to be used by Ireland, France, Belgium and The Netherlands where possible. The notional UK small scale DAB networks have been planned to operate at low powers, whilst the Irish and continental networks allocated in the band are planned to operate at substantially higher powers. The most dominant issues would be from incoming interference to the UK small scale DAB networks, rather than outgoing interference to the Irish and continental networks.

During this study more detailed information was supplied regarding the proposed usage of sub-band II by networks in France and Ireland. Analysis indicates that the majority of the notional UK small scale DAB multiplexes would remain viable, though at a reduced level of availability. There would be sufficient scope to adapt the plan where predicted interference is judged to be unacceptable.

Further work

Before any practical frequency plans for further small scale DAB networks can be developed, further information would be needed from the UK’s neighbours, and the UK would need to seek international coordination for some transmitter proposals.

We also anticipate that we would engage with the business radio community to seek to ensure that the technical requirements for protecting PMR services remain appropriate and do not unduly constrain the roll-out of small scale DAB.


Contents

Section Page 1 Introduction 1

2 Methodology & Assumptions 3

3 Service Selection 6

4 The Planning 8

5 Sub-Band II PMR Services 14

6 International Considerations 19

7 Sub-Band III Channel Availability 27

8 Discussion & Conclusions 30

Annex Page 1 Indicative coverage maps 33

2 Site data for a notional small scale DAB network 41

3 PMR Protection Calculations 57


1

Section 1

1 Introduction When Ofcom first considered the opportunities for implementing additional small DAB multiplexes in the UK, we carried out an initial study looking at frequency availability in the Manchester area. We concluded that it would be possible to make use of Band III, sub-band III blocks 10B, 11B and 11C. We looked at ways that the frequencies proposed could be used to allow those analogue radio services in the area which were not yet on DAB to be accommodated. We found that to achieve this, two DAB frequency blocks would be required over this relatively limited geographical area. If the plan were extended to serve other areas, it was apparent that additional spectrum, beyond that available in sub-band III, would be required.

This study considers the potential for additional spectrum to accommodate small scale DAB services. We conclude that it should be feasible to use blocks 7D, 8A, 8B, 9A, 9B and 9C (all in sub-band II), for small scale DAB services in certain areas of the UK. This spectrum was previously allocated to PMR services, but as part of the Ge06 Plan, the majority of the PMR services have migrated away from sub-band II. We expect some PMR usage to remain in these blocks in South Yorkshire, the English East Midlands, Merseyside and Aberdeen, perhaps until 2020. This will place a temporary limitation on the availability of the additional spectrum, and therefore implies a later deployment of small scale DAB within the north of England, the English Midlands, the northern Home Counties, and the north west of England.

This study finally considers the possible extension of small scale small scale DAB to the whole of the UK. Our approach has been to group existing analogue Community radio and small commercial radio services by area, with a view to examining the technical feasibility of developing a frequency plan which would allow them to be carried on small scale DAB multiplexes. Larger areas with many services (London, the English West Midlands, Manchester and Glasgow) have been split into smaller areas with the aim of ensuring sufficient capacity for current and future services. The plan has been developed around the use of six blocks, primarily the six sub-band II blocks mentioned above, supplemented with spectrum interleaved amongst the established DAB multiplexes where necessary.


2

A number of points have been identified in developing the notional six block plan. In particular, we note the following issues that are highlighted in this report:

• The importance of careful choice of transmission site to achieve ‘useful indoor’

coverage within the target area;

• In some areas, more than six blocks are required to avoid undue inter-block

interference;

• Some areas under this notional plan would remain unserved;

• There would be temporary limitations on deployment of small scale services due to

the need to protect the remaining PMR services in sub-band II;

• Where data is available, we examine the likely interactions between the proposed

DAB networks and the continent and Ireland; and

• Challenges in finding interleaved spectrum in sub-band III to assist with the issues

above.

Because the remaining PMR services within sub-band II need to be protected until 2020, the notional network developed in this study could not be fully implemented immediately. Analysis indicates that, of the 192 areas studied, 59 within the north of England, the English Midlands, the northern Home Counties and the north west of England would impact the remaining PMR services.

Additionally, it is likely that co-block interference from the continent and Ireland will further limit the coverage to adjacent areas in the south of England, East Anglia, and Northern Ireland.

Interleaved blocks may be used from sub-band III where required, although there is very limited capacity in many areas. There is a particular shortage of capacity in areas where it could help to avoid the impact on remaining PMR services within sub-band II.


3

Section 2

2 Methodology & Assumptions DAB coverage analysis has been performed using the ICS telecom predictive planning tool, using a Fresnel/Deygout 94 method and 50m Infoterra Digital Terrain Model data, as used by Ofcom broadcast radio planners.

Unwanted interference has been calculated for 1% time by assuming an earth radius of 28,550 km rather than 8,550 km, assumed for 50% time. The wanted field strength level has also been calculated for 1% time availability. The wanted field strength for 1% availability makes very little difference over short (wanted) distances, and allows common field strength predictions to be used both for wanted and interference, simplifying the planning process within ICS telecom.

Although signal levels are log-normally distributed according to location, for practicality when using ICS telecom, a simple power sum has been assumed for both wanted and interfering signals. This will result, if anything, in the practical network having slightly increased location availability compared to that predicted.

A co-channel protection ratio of 25dB has been assumed. This is derived from a receiver protection ratio of 10dB and a margin to protect to 99% location availability of 15dB.3 Field trials have indicated that it may be appropriate to use a protection ratio of 15dB. This reduction is largely attributed to a positive correlation between wanted and interfering field strengths. This difference in protection ratio does not generally impact upon planning decisions, but may result in practical coverage being slightly greater than predicted in interference limited areas. At the planning stage, the 25dB protection ratio is useful in understanding station interactions.

Coverage has been assessed to minimum field strengths of 54dBµV/m and 63dBµV/m, at 10m above ground level, corresponding to the accepted thresholds for ‘mobile’ and ‘useful indoor’ reception.

Each transmitter site has been nominally planned to operate at 100W ERP. In most cases, this nominal ERP is considered a good balance between the need to provide good coverage whilst limiting outgoing interference, thereby allowing reuse of channel blocks to serve adjacent areas. To improve coverage, in some cases, this ERP may be increased by 3dB or even 6dB, but generally has been adjusted downwards to meet coverage requirements or to limit outgoing interference.

3 The planning margin is derived theoretically as (4.0 x 2.33 x √2) = 13.2 dB, assuming both wanted and unwanted signals are Gaussian distributed with standard deviations of 4.0 dB, and are uncorrelated.


4

Many antenna patterns are possible, but for the purposes of this study, a selection of standard transmit antenna patterns has been used, as shown in figure 2.1.

Yagi

Figure 2.1 Standard Transmit Antennas, Horizontal Radiation Patterns

This study is primarily based around the use of six DAB channel blocks (7D, 8A, 8B, 9A, 9B and 9C), with the aim of identifying any particular difficulties associated with frequency reuse in a six block plan. It is recognised that some of these channel blocks cannot be utilised over the whole UK at present, due to the continued operation of co-channel PMR services in south Yorkshire, the English East Midlands, and Merseyside. Interleaved spectrum in sub-band III (blocks 10B to 12D) could be used to overcome difficulties in areas otherwise limited by UK or continental interference within the six block plan, or to allow additional small scale DAB service areas to be added. In a limited number of areas, the use of sub-band III blocks may allow implementation of small scale DAB where remaining PMR services require protection.

Dipole on Mast (10dB Front to Back ratio)

Dipole on Pole (4dB Front to Back ratio)

Dipole on Pole (6dB Front to Back ration)

Omnidirectional Panel Yagi


5

Adjacent channel interference (ACI) may create a ‘hole’ in coverage within a very short range of a transmitter site when attempting to receive services from other transmitter sites. Adjacent channel interference has not been specifically investigated when considering interactions between the six sub-band II blocks. Mitigation is frequently possible by careful selection of sites and antenna patterns, and this would need to be considered in the detailed planning and implementation phase.


6

Section 3

3 Service Selection The candidate services for small scale DAB were identified by running a query within the Ofcom technical licensing database, to create list of all community radio and small scale radio services not currently on DAB (as of Spring 2015). The candidate services were mapped to allow service groups and areas (forming the notional small scale DAB multiplexes) to be identified. The grouping is notional so as to inform this spectrum planning study only and does not represent how multiplexes would be arranged in any formal deployment of small scale DAB in the future.

By creating more groups in areas where there is a requirement for a larger number of services, it is possible to limit the number of services per multiplex to fit within practical bit rate limits.4 In these areas there is generally a large degree of coverage overlap. Figure 3.1 gives an indication of the number of services per notional small scale DAB multiplex considered in this study, based on the number of analogue-only stations in each area.

4 For a mix of bit rates up 128kbits at UEP3, it would be possible to implement up to nine stereo services per small scale DAB multiplex.


7

Figure 3.1: Number of services per notional multiplex



8

Section 4

4 The Planning The UK was split into areas as the plan developed. These areas were based on the station grouping areas and regions that could be planned independently. The region boundaries were based upon maximum co-block interference within an area rather than any physical or political boundaries, hence services in Wales were grouped with the South West and North West areas.

The coverage of each transmitter site currently used to provide a small commercial or Community analogue radio service within a group was assessed, and the best combination of sites selected to provide the composite DAB service.

From the list of standard antennas shown in figure 2.1 the most appropriate transmit antenna was selected to provide coverage in the desired area whilst limiting out of area interference. The ERP selected was generally 100W, though this was adjusted in some instances to limit out of area coverage or outgoing interference.

Figure 4.1: The planning areas

As each group was planned, the coverage was compared with the published FM coverage maps for the constituent stations. The coverage was assessed against the requirements for both ‘mobile’ and ‘useful indoor’ reception (54dBµV/m and 63dBµV/m at 10m a.g.l.). This equates to the protected 64dBµV/m published coverage threshold for FM community radio services.

To ensure ‘useful indoor’ coverage whilst operating with a limited ERP, small scale DAB transmitter sites generally need to be close to the area to be served. The sites used for small scale DAB in this study were selected from those already used to provide small radio services, some of which are not close to the target area. It may be possible to identify more suitable sites in the detailed planning stage.

Locations where more suitable sites may need to be found (or added) in order to improve coverage include Dorchester, Salisbury, Aylesbury, Colchester, Banbury, Ludlow and Wigan.



9

This is illustrated in figure 4.2. The site for the Banbury area is midway between Banbury and Brackley. Although ‘mobile’ DAB coverage would be achieved over the whole area, two sites could be placed individually to provide both Banbury and Brackley with ‘useful indoor’ coverage.

Figure 4.2: Banbury coverage (‘Useful Indoors’ and ‘Mobile’)

Community radio stations generally operate at a maximum of 25W ERP, whilst the majority of small FM radio services operate at 100W ERP or less. Individually, each station has limited coverage, but when combined together to create a small scale DAB multiplex, a larger aggregate area would be served. This is illustrated, for the Teesside area, in figure 4.3. In areas where more than one transmitter site contributes to DAB coverage, there is the additional benefit of a decrease in location variability (i.e. less need to move the receiver in order to achieve robust reception).

Figure 4.3: Combined sites - multiplex area For the few small FM radio services that operate at ERPs greater than 100W, it may be necessary to add additional sites so that coverage can be maintained, whilst limiting each small scale DAB site to around 100W ERP. This is illustrated, for the King’s Lynn area, in figure 4.4.




‘Useful Indoors’ ‘mobile’


10

Figure 4.4: Additional site - King’s Lynn

The FM service for King’s Lynn operates at 2.1kW ERP. In the notional small scale DAB plan, the existing site at Great Massingham operates at 100W ERP and a new site is added, also operating at 100W ERP. Should it be desired to provide more ‘useful indoor’ coverage to Swaffham and Fakenham, additional sites could be added.

Similarly, within this study, additional sites have been added to serve Stratford upon Avon (FM service 1.5kW ERP, 14km to the south) and Lancaster/Morecambe (FM service 1.6kW ERP, 30km across Morecambe Bay), as shown in figures 4.5 and 4.6.

Figures 4.5 and 4.6: Additional Sites – Stratford upon Avon and Lancaster & Morecambe In order to provide robust coverage within London, several additional sites have been added. Figure 4.7 shows the existing and added sites, to provide ‘useful indoor’ coverage. Further sites would need to be added to improve coverage within north-west London.


Added Site

Existing Site




11

Figure 4.7: London ‘Useful Indoor’ Coverage - Added and Existing Sites The sub-band II block selected for each multiplex was based on a judgement of the likely reuse distance, but taking advantage of the terrain to allow (where possible) blocks to be reused over shorter distances. Efficient use of spectrum is demonstrated by adequate coverage being achieved, whilst being slightly limited by co-block interference.

Most areas required two or three planning iterations, where block usage, ERP or transmit antenna patterns were adjusted, in order to achieve the desired predicted coverage.

To understand coverage interactions, and to be consistent in approach, a co-channel protection ratio of 25dB was assumed. Ofcom planning standards specify a protection ratio of 25dB but relaxes this by 10dB due to the expected correlation between wanted and unwanted signals. The ITU proposes a protection ratio of 15dB. Whilst such a relaxation to 15dB was considered when deciding whether some specific interactions could be tolerated, in general, the use of 25dB has not impacted upon planning decisions. Figure 4.8 shows predicted interference between multiplexes using block 9A, in the Midlands, considered with protection ratios of 25dB and 15dB.

Added Site

Existing Site



12

Figure 4.8 Co-channel interference considered at 25dB and 15dB protection ratio In developing a notional frequency plan the whole UK, using six frequency blocks (7D, 8A, 8B, 9A, 9B and 9C), it has been found that there are a few areas where additional spectrum is required. Particularly ‘congested areas’ are found in the Bristol area, the region around Manchester, Cheshire, Merseyside and the English East Midlands. Interleaved blocks in sub-band III may be used to ease this congestion in the following areas:

• It is assumed that block 11C is used to serve Weston-super-Mare. This is the block previously used for the Cardiff & Newport local multiplex.

• In line with the findings of the initial Manchester study, blocks 11B and 11C would be suitable to serve Warrington and Tameside following the planned frequency changes for the Liverpool and Manchester multiplexes.

• Ideally, an additional block is required in the East Midlands, for Coalville. An initial assessment indicates that block 10D may be suitable. This is the block used for the Herts, Beds and Bucks local multiplex.

If small scale small scale DAB services are to be launched in the English midlands and the north and north west of England whilst PMR usage continues within the same spectrum in south Yorkshire, the English East Midlands and Merseyside, then additional usage of available blocks within sub-band III may assist.

Coverage Loss



25dB PR 15dB PR


13

This Plan has been developed to address the question of whether existing community radio and small commercial services could be technically accommodated on DAB. However, no planning has been carried out in areas where such analogue services do not exist. Therefore the following areas are amongst those unserved by this notional sub-band II plan:

North Devon, Mid Wales, West Wales, Maidstone, Sevenoaks, Tonbridge, Tunbridge Wells, Rye, Dover, Chester, Bishop's Stortford, Milton Keynes, Thetford, Peterborough, Sleaford, Skegness, Louth, York, Scarborough, Bridlington, Whitby, Carlisle, West Cumbria, Melrose/Hawick, Dumfries, Northumberland & Inverness

These areas are shown in figure 4.9 as dots, along with the ‘mobile’ coverage achieved for the six block sub-band II plan. A future plan might be needed to identify how / if these areas might also be served by sub-band II if there is evidence of demand from potential services in these areas.

Figure 4.9 Areas unserved in the sub-band II plan

Locations unserved in notional sub-band

II plan (‘mobile’ coverage)



14

Section 5

5 Sub-Band II PMR Services Under the terms of their licences, PMR services may continue to use the sub-band II blocks shown in table 5.1 until 2020.

Table 5.1: PMR SB II block usage until 2020 As part of this study, we assessed the likely restrictions to small scale DAB from the continued use of sub-band II blocks for PMR. For the basis of this assessment, we used ITU Rec R-1546 as the propagation model and assumed that the PMR base stations use omnidirectional transmit and receive antennas. This approach, which is based on exclusion distances, is recognised by the PMR community.

An alternative approach has been used in this study. This approach uses the same prediction model for PMR services as is currently used to predict the DAB coverage. The approach takes the likely base station transmit/receive antenna into account. This alternative approach, if acceptable, may result is less onerous restrictions to small scale DAB roll out, whilst providing the necessary protection to the remaining PMR services.

The assumed basis for the protection of PMR services is that the effective5 interfering DAB field strength should not exceed 27dBµV/m, as seen by either the PMR base station or mobile antenna. A derivation of this limit is provided in Annex 3.

To protect PMR mobile reception, a combined DAB field strength of more than 27dBµV/m should not exist over the service area of the PMR service. Because several DAB signals may combine at any given location, the level of any individual component signal should be lower. Ideally, an appropriate statistical summation, taking into account location variability, should be used for this assessment.

As the service area details for the PMR services were not available, the transmitted (base station) service areas for the South Yorkshire/East Midlands and Merseyside networks have been predicted, based on the licence parameters, highlighted in Annex 3. The service area

5 Taking the receiving antenna directivity into account.

Area Use DAB block

South Yorkshire & East Midland

Base Station Receive 7D, 8A, 8D

Mobile Receive 9A, 9B

Merseyside Base Station Receive 8B

Mobile Receive 9B, 9C

Aberdeen Base Station Receive 8B

Mobile Receive 9B


15

would be within the region where the field strength delivered for 50% time, is predicted to be 19dBµV/m6, at 1.5m above ground level.

Figure 5.1 shows the likely service areas for the South Yorkshire/East Midlands and Merseyside networks. Based on the prediction, possible areas to be protected have been identified, however further clarification should be sought from the PMR operators regarding the service area and the site technical parameters.

Figure 5.1 Likely areas for PMR mobile protection from DAB (power summation greater than 27dBµV/m) To protect PMR base station reception, a combined effective DAB field strength (taking into account receiving antenna directivity) of more than 27dBµV/m should not exist at any receive site. Again, as several DAB signals may combine, the level of component signals must be lower than this value where more than one co-channel DAB signal contributes to the ‘unwanted’ field.

This is a point-to-point limitation (i.e. DAB transmitter to PMR base station) based on the DAB station parameters. Consequently, it is not possible to definitively calculate DAB transmitter exclusion areas. As a guide, predictions have been performed in the reverse direction to establish where 27dBµV/m is received, for 1% time, at a height of 60m a.g.l7., for 100W ERP8 transmitted from each base station, using the base station antenna.

6 19dBµV/m, recognised service threshold by Ofcom. 7 90% of the antennas in the plan are at 60m or less. 8 100W being the maximum ERP used

9B & 9C

9A & 9B



16

Figure 5.2 shows the resulting possible exclusion areas to protect reception at base stations within the South Yorkshire/East Midlands and Merseyside PMR networks.

Figure 5.2: Possible areas for PMR base station protection from DAB (power summation greater than 27dBµV/m) Comparing the predictions in figures 5.1 and 5.2, it is likely that the restrictions to protect reception at the PMR base stations within blocks 7D, 8A and 8B (i.e. to the base station receiver) will be most onerous, but will depend upon the actual small scale DAB site parameters. The acceptability of the possible interference to the PMR service can only be established at the detailed DAB site planning stage.

The same analysis could be applied to protecting the Aberdeen PMR services within blocks 8B and 9B; however it has been possible to avoid using these channels for small scale DAB in the east of Scotland as other frequencies are available. The terrain in Scotland allows these channels to be used by DAB to the west without interfering with PMR. Furthermore, sub-band III spectrum is available in most of the area.

8B

7D, 8A & 8B



17

For each small scale small scale DAB service on blocks relevant to the PMR services, the 1% time field strength over the PMR service area, or received by the PMR base stations, has been assessed against the likelihood of a combined 27dBµV/m being exceeded. As several DAB signals may combine, the level of component signals should typically be lower by up to 10dB.

Of the 192 notional small scale DAB networks planned as part of this study, it is estimated that 59 might in principle impact upon the South Yorkshire/East Midlands or Merseyside PMR networks. These numbers are summarised in Table 5.2.

PMR Network small scale DAB Networks

Total Comment

South Yorkshire/East Midlands Mobiles 21 One small scale DAB Network may impact both PMR Networks

South Yorkshire/East Midlands Base Stations

28 49

Merseyside Mobiles 11

Merseyside Base Stations 0 11

Table 5.2 The number of small scale DAB Multiplexes Impacting PMR

The location of the notional small scale DAB networks that might have an impact on PMR networks are shown in figure 5.3.


18

Figure 5.3 small scale DAB Multiplexes Notionally Impacting PMR The notional small scale DAB areas that might have an impact on the remaining PMR services are outlined in the site data, provided in Annex 2.



19

Section 6

6 International Considerations General

International DAB frequency coordination is governed by the ITU Geneva 2006 agreement (Ge06). This contains allocated rights for DAB and Digital Terrestrial Television (DTT) for the UK and neighbouring administrations. It also allows for the use of other services such as PMR in VHF Band III.

The six DAB blocks being considered for small scale DAB are all allocated in Ireland and the continent for DAB or DTT in Ge06. At the time of writing, very few of these services have been implemented. However, any UK small scale DAB implementation would need to protect these allocations, and would not be able to restrict their implementation. This will generally mean that small scale DAB services located near to the UK coast and Northern Ireland border will be subjected to higher levels of incoming interference than in other parts of UK.

At the present time, the UK has no international rights to implement small scale DAB services and in order to do this would need to seek agreement from neighbouring countries where those services might put more than a defined signal level into those countries. The Ge06 agreement was formulated on the basis of equitable access to spectrum. As a consequence, it is likely that our neighbours would also wish to negotiate agreement for their own layer of small scale DAB or similar applications.

Due to the limited amount of sub-band II spectrum, and the number of administrations requiring services within it, it may be difficult to achieve the desired number of small scale DAB services in some areas of the UK. This is particularly so in Kent (and to a slightly lesser extent Essex, Sussex and Suffolk) where the UK would be seeking use of the same spectrum as France, Belgium and the Netherlands. The short distance between borders and unobstructed sea path means that frequency reuse is extremely difficult.


20

Outgoing Interference to France, Belgium and The Netherlands

To assess the acceptability of the notional UK small scale DAB network to the French, Belgian and Dutch administrations, ITU Rec R-1546 calculations have been performed, to assess the power sum9 of the UK signals for each sub-band II block (7D, 8A, 8B, 9A, 9B & 9C) at test points along the continental coast. The test points are shown in figure 6.1.

Figure 6.1 Continental coastal test Points Although the ITU coordination trigger limit10 is 12dBµV/m, coordination agreements with French, Belgian and Dutch administrations could be sought for power sums less than 39dBµV/m (for coordination with other DAB services) or 33dBµV/m (where coordination is sought with DTT services). This approach is consistent with that adopted in other bands, and would reduce the number of small scale multiplexes that we would need to coordinate with our neighbours.

Nevertheless, several locations within our notional network would still exceed these levels and may require some mitigating measures. Table 6.1 summarises the locations where this might be necessary, and some potential mitigating measures.

9 Bonn Summation as detailed in the Weisbaden 1995 Agreement, whereby interferers, to one decimal point, are power summed in order of magnitude, until a change of less than 0.5dB is detected. 0.5dB is then added to the resulting power sum. 10 The trigger limit is the level below which we do not need to seek coordination with neighbouring countries



21

Block/Test Point Summation dBµV/m Cause: and possible migitation

7D

F41 39.04 Portsmouth: Change from Omni to Directional Aerial.

Eastbourne: 2dB reduction in power.

Hastings: 2dB reduction in power.

F44 39.6

F46 40.15

8A

F30 38 (Maximum)

8B

F30 40.08 Poole: Change from Omni to Directional Aerial

F31 40.05

9A

F26 40.19 Torbay: Change from Omni to Directional Aerial

F27 41.19

9B

F26 41.17

Dorchester: 7dB reduction by combination of Omni to Directional aerial and power reduction.

F27 45.13

F28 40.18

F29 41.79

F30 41.77

9C

F27 40.77 Exmouth: Change from Omni to Directional Aerial

F54 41.07 Folkstone: Change from Omni to Directional Aerial

Table 6.1 Bonn 1546 Power Sum to continental coastal Test Points


22

Constraints from France

To reduce continental interactions, frequency blocks have, where possible, been avoided for UK coastal sites that are likely to be heavily used in adjacent locations by France, Belgium and the Netherlands11. Because all six sub-band II blocks are required in the notional UK small scale DAB plan, the continental co-channel blocks have been used further along the coast or inland. During this study we have obtained more detailed information regarding France’s Band III frequency requirement, although the details of the French plans are subject to change and further development. The information currently available covers one of two regional networks, two national networks and one local layer (Lille, Haute Normandie, Basse Normandie, and Bretagne). All are using sub-band II & sub-band III blocks in areas adjacent to the UK. We currently have no information on the planned second regional network or second local layer in France. However the majority of proposed French DAB sites proposed have an ERP of around 10kW. Therefore, it is likely that the main issues would be from incoming interference to the UK small scale DAB networks, rather than outgoing interference to the French networks.

The site locations of sub-band II frequency blocks proposed for the French networks, and the UK blocks proposed within this study, are shown in Figure 6.2. The UK locations and French sites with significant interactions are named.

Figure 6.2 France to UK Interference and Block Usage From Figure 6.2, it can be seen that use of blocks 8A and 8B for small scale DAB has been avoided in the Strait of Dover area, whilst blocks 9A, 9B and 9C have been avoided along

11 Likely continental DAB block usage taken from ‘Sub-CNG 1-1 Iteration4: planning results. Confédération Suisse’



23

the south Cornwall coast. As these blocks cannot be completely avoided, they have been used at greater distances or where terrain protection may assist in interference mitigation.

The small scale DAB networks in this study have been intentionally planned to be interference limited, considering a co-block protection ratio of 25dB. This has been done to ensure that blocks are used optimally, but with the expectation that ‘mobile’ coverage in outlying areas may actually be better, when considering the relaxed ‘real world’ protection ratio of 15dB.

Based on our current understanding of proposed French networks, only blocks 7D, 8A and 8B are predicted to be significantly impacted in the UK. The continental networks considered are based on currently anticipated requirements, and it may be possible to negotiate further restrictions. Where this is not possible, practical transmitter antenna patterns actually used in France may offer some mitigation that could reduce the impact of interference on the UK small scale multiplexes.


24

Constraints from, and to, the Republic of Ireland

The implications of the UK’s notional small scale DAB network to - and from - the Republic of Ireland have been assessed against DAB ‘requirement’ files submitted by the Irish administration.

The site locations and sub-band II frequency blocks planned for the UK and Irish networks are shown in Figure 6.7. Sites where notable interactions are predicted are named.

Figure 6.7 UK / Ireland Interactions The Irish network operates from main station and smaller sites, with ERPs ranging from 100W to 25kW. Predictions indicate that the notional small scale DAB network would cause only minimal impact upon the Irish network, though this would need to be considered further at the detailed planning and implementation phase.

Interference to the UK networks has been considered at 1% time for a protection ratio of 25dB. With a protection ratio of 15dB, in some instances, the impact on coverage of incoming interference may be acceptable. For lower time availability, coverage (generally ‘mobile’) often increases, which suggests that the ‘real world’ coverage would be somewhat better than our predictions. For example, in figure 6.8 the interference from Ireland’s Cairn Hill allocation to sites in Northern Ireland using block 9A is assessed with protection ratios of 15dB or 25dB, and with 99% or 50% time availability.



25

Figure 6.8 Cairn Hill interference with Protection Ratio of 15dB or 50% time availability Figure 6.8 shows that whilst the time-varying incoming interference to the notional small scale DAB multiplex for Belfast may be acceptable, the interference to the Omagh and Enniskillen networks is unlikely to be acceptable, and alternative solutions would need to be identified.

Our initial study suggests that the use of sub-band II frequencies will be challenging in Northern Ireland, and we may need to use alternative spectrum. PMR services do not operate within sub-band I (channels 5 & 6) in Northern Ireland. Therefore it may be possible to use this spectrum to overcome interference or to provide additional services. Interleaved capacity with sub-band III might also be used in addition to, or in place of, sub-band II.

PR 25dB & 1%

PR 15dB & 1%

PR 15dB & 50%





26

Constraints from Belgium and The Netherlands

Figure 6.9 Sub-Band II usage in The Netherlands and Belgium

The Netherlands presently has a number of DTT allocations on their coast. Channel 8 is planned for the North Holland and South Holland provinces. Channel 9 is allocated to the coastal areas between Belgium and South Holland and north of North Holland. These allocations will place significant constraints on the use of these blocks in the east of the UK. Channel 7 is allocated to an inland area of the Netherlands that is not expected to be problematic. Any interference from The Netherlands would be in addition to that previously discussed from France. Due to its proximity, it is anticipated that French interference will generally dominate. The situation will need to be analysed once more definite information becomes available.

Based on current information, it is understood that channels 7, 8 and 9 may not be widely used for high power services in Belgium. Although this will also need to be considered further when more detailed information becomes available.



27

Section 7

7 Sub-Band III Channel Availability In developing our notional small scale DAB network, we have concluded that it will be necessary to use interleaved spectrum from sub-band III (which is also used to provide local DAB services) in some areas. Our notional plan makes use of sub-band III blocks for north Somerset, south Manchester and the English East Midlands (where six blocks are not sufficient). We expect that additional sub-band III blocks will be required where additional small scale DAB areas are required, continental limitations are imposed, or where there is an ongoing requirement to share the sub-band II spectrum with the remaining PMR services.

Although it is subject to change, the planned usage of sub-band III for the local DAB networks is shown in figure 7.1.

Figure 7.1: Sub-band III block usage for local DAB networks



28

When developing the notional six block plan for small scale DAB, we assessed the extent of potentially interfering field strengths in order to establish which sub-band III blocks might be available.

This assessment was carried out for interfering field strengths of 29dBµV/m (i.e. a protected wanted field strength of 54dBµV/m with a 25dB protection ratio) or 39dBµV/m (protected field strength of 54dBµV/m with a 15dB ‘real world’ or relaxed protection ratio). From this, a judgement was made of the interleaved usage which was likely to be acceptable. However, before more firm decisions of acceptability can be made, a more rigorous assessment of the compatibility with existing local DAB services would need to be carried out.

As an example, figure 7.2 and table 7.1 highlight the selection of a possible sub-band III channel for a notional Wetherby small scale DAB multiplex. The maps illustrates the area over which the Wetherby small scale multiplex would put down more than 29dBµV/m, and the areas where the multiplex could cause interference to co-channel multiplexes elsewhere.

Figure 7.2 Selection of sub-band III block for Wetherby small scale DAB

29dBµV/m



29

SBIII Block Usage Comment

10B Derbyshire *** Possible ***

10C North Yorkshire Not available

10D Humberside Not available

11B Bradford/Teesside Not available

11C South Yorkshire Not available

12A Lincolnshire/Lancashire Not available

12C Nottingham Possible, but adjacent to the local block within Leeds Area

12D Leeds Not available

Table 7.1 Selection of Sub-Band III Block for Wetherby small scale DAB

Note: Blocks 11A, 11D and 12B are used for national DAB services, so are not available for small scale DAB.

Table 7.1 suggests that block 10B may be available for use in Wetherby. This potential allocation would need to be investigated further to ensure that the existing Derbyshire DAB multiplex, which uses the same frequency, would be sufficiently protected. This assessment would also need to take into account any further expansion of the Derbyshire local multiplex into areas such as Chesterfield.

Our analysis suggests that in many areas, a sub-band III block would potentially be available for small scale DAB to use. The exceptions are the English East Midlands, Berkshire, Bedfordshire and Buckinghamshire, where we could not identify any sub-band III spectrum.

While PMR services continue to operate in sub-band II, any interim use of available sub-band III frequencies in the English Midlands and the north of England which would limit frequency availability elsewhere until PMR services have vacated this spectrum.

In the English East Midlands, Bedfordshire, Buckinghamshire and Hertfordshire, no sub-band III capacity can be found without impacting upon local DAB services.


30

Section 8

8 Discussion & Conclusions Assumptions

The notional small scale DAB multiplexes described in this study have been planned around the use of sites currently used to provide community and small commercial radio services. Rather than using all sites, the best technical combination of sites has been selected to provide the required composite DAB service.

Our starting assumption is that the small scale DAB sites would typically operate at up to 100W ERP. This is sufficient to provide good coverage over a range of about five kilometres which is similar to that provided by the majority of community services. To achieve ‘useful indoor’ coverage, it is necessary for the sites to be near to the centre of the service area. Whilst the majority of low power FM sites are suitable, in some areas more suitable sites would ideally need to be found or additional sites provided. In intersection areas, where more than one transmitter provides coverage, an additional advantage would be gained through a reduction in location variability (which should improve reliability of reception).

Results

Using six blocks (sub-band II block 7A, 8A, 8B, 9A, 9B and 9C) to serve many distinct areas over the extent of the UK and Northern Ireland is generally successful. ‘Congested’ areas have been identified (North Somerset, South Manchester and the East Midlands) where additional spectrum (sub-band III) would be required.

The notional small scale DAB plan has been based around current low power FM requirements. Many areas are not covered by these analogue services and therefore have not been considered in this study. The ‘six block plan’ could be extended to many of these and other areas, though in congested areas, the use of sub-band III spectrum would also need to be investigated.

Temporary PMR constraints

Although the majority of PMR services have migrated away from sub-band II, any future deployment of small scale DAB will need to take into account the presence of PMR in south Yorkshire, the east midlands, Merseyside and Aberdeen until perhaps 2020. This will place a temporary limitation on sub-band II spectrum availability, placing constraints on the roll out of small scale DAB within the North of England, the English midlands, the northern home counties and north west England. The limitations imposed by PMR in the Aberdeen area should not impact upon small scale DAB roll out. Analysis within this study indicates that a third of areas investigated may not be compatible with the remaining PMR services.

The approach traditionally taken to ensure compatibility with PMR services, including the methods employed and areas to be protected, may benefit from review.


31

International compatibility and coordination

Because the notional small scale DAB sites operate at low power, interference to the continent and Ireland should be minimal. Analysis of the power sum from each sub-band III block (7D, 8A, 8B, 9A, 9B & 9C) to test points along the continental coast, indicate that coordination agreements for outgoing interference with French, Belgian and Dutch administrations could be possible.

Where possible, blocks have been avoided for UK coastal sites that are planned to be used in adjacent locations by France, Belgium and The Netherlands. As the proposed continental and Irish networks are planned to operate at considerably higher powers, the impact upon the small scale DAB networks may be significant, although much will depend on what is actually implemented in other countries.

From the proposed French network, blocks 7D, 8A and 8B are significantly impacted on the south and south east coast if we use traditional DAB planning parameters. We plan to carry out further work to assess what planning parameters, such as location variability, are appropriate for small scale DAB.12. We also plan to engage in more detail with neighbouring administrations about their plans to implement DAB or other networks in Band III. By negotiating restrictions, especially for French coastal transmitter sites, the French interference constraints may be improved. Information is yet to be received regarding the second regional and local French networks.

The proposed Irish networks operate on four of the sub-band II blocks (7D, 8A, 9A 9C) as well as DTT. By amending our planning parameters to take ‘real world’ conditions into account (i.e. considering a reduction in location availability) and negotiating further restrictions, the majority of small scale DAB proposals in challenging areas could be viable13. As PMR services do not operate within sub-band I (channels 5 & 6) in Northern Ireland, this capacity could be considered for use to overcome interference or to provide additional services.

Detailed information is not available from Belgium or The Netherlands. However, it is understood that channel 8 would be used by the Dutch adjacent to the coast and channels 7, 8 and 9 may not be widely used for high power services in Belgium. Where possible, channel 8 has been avoided in the east of England region. The situation will need to be analysed when more detailed information becomes available.

It is possible that neighbouring administrations will wish to implement their own small scale DAB services. While this will place an extra demand on spectrum, it might allow a common group of blocks be to agreed, where low power implementation is simplified.

Indoor coverage is generally protected against interference and this should not change. The need to use spectrum efficiently means that mobile coverage is often limited by co-block interference. This will result in coverage changes occurring as more multiplexes come on air over time. This coverage ‘breathing’ cannot be avoided, so the detailed frequency planning

12 The small scale DAB proposal in this study for Chichester would need to be re-addressed. 13 The small scale DAB proposal in this study for Omagh & Enniskillen and Downpatrick would need to be re-addressed.


32

will need to establish that the worst case mobile coverage (modelled at 1% time) is acceptable. Analysing coverage with two co-block protection ratios or relaxing the time availability would allow the extent of interference to be understood and accepted.

Additional spectrum in sub-band III is available in many areas

In developing the six block plan, the availability of sub-band III blocks has been investigated. Whilst in many areas a possible sub-band III block can be found, in areas such as the English east midlands, Bedfordshire, Buckinghamshire and Hertfordshire, no sub-band III capacity can be found.

While PMR services are still present in sub-band II, we would need to make use of sub-band III frequencies in many adjacent areas. Sub-band III blocks may provide a solution in areas of congestion, but can only provide a limited solution until the remaining PMR services have vacated the sub-band II spectrum. In more detailed investigations into sub-band III availability, the operators of existing services may need to be consulted on the acceptability of specific proposals.


33

Annex 1

1 Indicative coverage maps



Mobile: 54dBµV/m

Indoor: 63dBµV/m


34



Mobile: 54dBµV/m

Indoor: 63dBµV/m


35



Mobile: 54dBµV/m

Indoor: 63dBµV/m


36



Mobile: 54dBµV/m

Indoor: 63dBµV/m


37



Mobile: 54dBµV/m

Indoor: 63dBµV/m


38



Mobile: 54dBµV/m

Indoor: 63dBµV/m


39



Mobile: 54dBµV/m

Indoor: 63dBµV/m


40



Mobile: 54dBµV/m

Indoor: 63dBµV/m


41

Annex 2

2 Site data for a notional small scale DAB network

ICS Stn Callsign Multiplex Service Area TX Site Service X Y

Site Hgt m a.s.l.

Antenna Hgt m ERP W Omni/Dir Block

Frequency MHz Network ID Comment PMR Impact

1 SW2_CR114 S Cornwall Falmouth Penryn The Source 176900 34700 110 20 100 Dir 7D 194.064 SS_Southwest_22 SW2_CR248 S Cornwall Truro Truro CHBN 179800 45300 93 25 100 Dir 7D 194.064 SS_Southwest_23 SW2_CR252H S Cornwall South Cornwall Tregony The Hub 191250 45650 89 15 100 Omni 7D 194.064 SS_Southwest_24 SW2_CR252M S Cornwall Mevagissey Mevagissey The Hub 201440 45593 74 8 100 Dir 7D 194.064 SS_Southwest_25 SW2_CR252S S Cornwall ST Mawes St Mawes The Hub 184992 33598 59 12 100 Dir 7D 194.064 SS_Southwest_26 SW2_CR115 S Cornwall S. Cornwall St Austell RFC Radio St Austell 202500 51100 77 15 100 Dir 7D 194.064 SS_Southwest_28 SW1_CR249S Penzance St Just St Just Penwith Radio 137900 30800 156 12 100 Dir 8B 197.648 SS_Southwest_19 SW1_CR249P Penzance Penzance Penzance Penwith Radio 147350 29350 0 22 100 Dir 8B 197.648 SS_Southwest_112 SW3_AL328 Plymouth Plymouth Plymouth Radio Plymouth 249700 51700 116 66 100 Dir 8A 195.936 SS_Southwest_3 Extra site for Saltash needed15 SW5_AL303 Torbay Torbay Totnes Palm FM 285700 61900 175 80 100 Omni 9A 202.928 SS_Southwest_517 SW4_CR236 Exeter Exmouth Exmouth Bay FM Radio 303441 83891 123 30 100 Omni 9C 206.352 SS_Southwest_418 SW4_AL318 Exeter Exeter Exmouth Radio Exeter 289800 92200 92 40 100 Omni 9C 206.352 SS_Southwest_420 SW32_AL260P Minehead Porlock Porlock The Breeze 288300 146200 174 21 100 Dir 9A 202.928 SS_Southwest_3221 SW32_AL260M Minehead Minehead Minehead North The Breeze 296500 147200 159 15 100 Dir 9A 202.928 SS_Southwest_3223 SW6_CR109 Taunton Wiveliscombe Wiveliscombe 10Radio 310600 126250 147 10 100 Omni 7D 194.064 SS_Southwest_6

24 SW6_CR241 Taunton TauntonMusgrove Park Hospital Apple 321500 124100 20 26 100 Dir 7D 194.064 SS_Southwest_6

27 SW7_CR240 Bridgewater Bridgewater Westfield House Access FM 329350 136750 10 38 100 Dir 8A 195.936 SS_Southwest_7

28 SW17_AL249Weston Super-Mare

Weston Super-Mare

Weston Super-Mare The Breeze 332507 162678 105 42 100 Dir 11C 220.352 SS_Southwest_17 SB III Block

29 SW16_CR239 Cheddar Cheddar Fry's Hill Pulse 343600 155700 234 20 50 Dir 8B 197.648 SS_Southwest_1630 SW15_CR117 Glastonbury Glastonbury Glastonbury Glastonbury FM 348600 138100 9 12 100 Omni 9C 206.352 SS_Southwest_1531 SW10_CR235Y Yeovil Yeovil Charlock Hill The Breeze 361404 117882 144 17 100 Dir 9A 202.928 SS_Southwest_1033 SW10_CR235S Yeovil Sherborne Sherborne Radio Sherborne 364000 117900 115 17 100 Omni 9A 202.928 SS_Southwest_10

35 SW8_AL154RDorchester&Weymouth

Dorchester & Weymouth Bridport Wessex FM 345305 91484 68 35 100 Dir 9B 204.64 SS_Southwest_8

36 SW8_AL154BDorchester&Weymouth

Dorchester & Weymouth Bincombe Wessex FM 368703 84785 148 45 100 Omni 9B 204.64 SS_Southwest_8

Better site serving Dorchester 'indoors' needed

38 SW21_CR232 Bristol North Bristol North Bradley Stoke Bradley Stoke 361204 182477 67 14 100 Omni 9C 206.352 SS_Southwest_2139 SW20_AL247 Bristol South Bristol Pur Down The Breeze 361004 176377 82 65 100 Omni 9A 202.928 SS_Southwest_2040 SW20_CR116 Bristol South Bristol Bristol Ujima Radio 360300 174000 13 51 100 Omni 9A 202.928 SS_Southwest_2043 SW19_AL248 Bath Bath Bath The Breeze 376902 165478 177 41 100 Dir 8A 195.936 SS_Southwest_1944 SW18_CR113 Midsomer Midsomer Midsomer Somer Valley FM 368103 156279 152 17 100 Omni 7D 194.064 SS_Southwest_1845 SW9_CR230 Frome Frome Frome Frome FM 377400 147800 107 12 100 Dir 9B 204.64 SS_Southwest_947 SW9_CR229 Frome Warminster Warminster WCR 387300 145100 111 19 100 Omni 9B 204.64 SS_Southwest_949 SW11_AL179B Shaftesbury Blandford North Dorset The Breeze 388799 107100 64 15 100 Omni 8A 195.936 SS_Southwest_1151 SW11_AL179S Shaftesbury Shaftesbury Shaftesbury The Breeze 386401 123481 211 35 100 Dir 8A 195.936 SS_Southwest_1153 SW13_CR063 Verwood Verwood Cranevalley Golf Forest FM 406699 108983 58 15 100 Omni 7D 194.064 SS_Southwest_13


42


Site Hgt m a.s.l.

Antenna Hgt m a.g.l. ERP W Omni/Dir Block


54 SW12_CR120Poole & Bournemouth Poole Poole Hot Radio 403400 93300 64 25 100 Omni 8B 197.648 SS_Southwest_12

55 SW12_CR086Poole & Bournemouth Bournemouth

Poole House_Universit Hope FM 407300 93700 50 31 100 Omni 8B 197.648 SS_Southwest_12

57 SW14_AL145 Salisbury Salisbury Camp Hill Spire FM 411199 133681 135 21 100 Omni 9C 206.352 SS_Southwest_14Better site serving Salisbury 'indoors' needed

58 SW14_CR092 Salisbury Bulford Bulford Salisbury Plain 419498 142880 194 24 100 Omni 9C 206.352 SS_Southwest_1460 SW23_CR231 Devizes Devizes Devizes Fantasy Radio 400600 161300 128 20 100 Omni 8B 197.648 SS_Southwest_2361 SW22_AL304 Swindon Swindon Blunsdom Jack FM 414299 189976 146 45 100 Omni 7D 194.064 SS_Southwest_2262 SW22_CR119 Swindon Swindon Brunel Tower Swindon FM 414899 184676 100 89 100 Omni 7D 194.064 SS_Southwest_2263 SW24_CR054 Gloucester Gloucester Clapham Court Gloucester FM 383502 218873 15 36 100 Omni 9A 202.928 SS_Southwest_2464 SW25_AL225 Cheltenham Cheltenham Cheltenham The Breeze 394800 221673 68 57 100 Omni 8A 195.936 SS_Southwest_2565 SW26_CR233 Winchcombe Winchcombe Winchcombe Radio 402300 228573 96 13 100 Omni 9C 206.352 SS_Southwest_261 S1_AL317 Andover Andover Andover The Breeze 437200 144550 118 10 100 Omni 8A 195.936 SS_South_12 S1_CR093 Andover Ludgershall Tidworth Castledown 425300 150200 135 9 100 Omni 8A 195.936 SS_South_14 S4_AL1104V Isle of Wight IOW Ventnor Isle of Wight 456700 78300 208 40 40 Dir 8A 195.936 SS_South_45 S4_AL1104R Isle of Wight IOW Ryde Pier Isle of Wight 459300 93700 0 13 50 Dir 8A 195.936 SS_South_46 S4_AL1104C Isle of Wight IOW Cowes Isle of Wight 449600 96300 4 10 100 Dir 8A 195.936 SS_South_47 S4_AL1104H Isle of Wight IOW Chillerton Down Isle of Wight 447500 83500 165 140 25 Omni 8A 195.936 SS_South_410 S3_AL239 Southampton Southampton Chilworth The Breeze 440600 118000 85 24 100 Dir 9A 202.928 SS_South_311 S3_CR008 Southampton Southampton Midanbury Unity 101 444700 114200 59 14 100 Omni 9A 202.928 SS_South_3

12 S3_CR213 Southampton SouthamptonSouthampton_Solent_Uni VOICE FM 442200 112200 10 33 100 Omni 9A 202.928 SS_South_3

13 S3_CR009 Southampton Southampton Hedge End Skyline Gold 448000 112800 49 20 100 Dir 9A 202.928 SS_South_3Better site serving Fareham needed ?

15 S2_AL241 Winchester Winchester Crabwood Farm II The Breeze 444950 129450 150 42 100 Omni 9B 204.64 SS_South_2

16 S10_AL256HNewbury & Hungerford Hungerford Hungerford The Breeze 433800 167401 128 17 100 Omni 9A 202.928 SS_South_10

17 S10_AL256NNewbury & Hungerford Newbury Newbury The Breeze 445250 164800 126 46 100 Omni 9A 202.928 SS_South_10

19 S5_AL238 Portsmouth Portsmouth Fort Southwick The Breeze 462600 106900 117 18 100 Omni 7D 194.064 SS_South_520 S5_CR006 Portsmouth Portsmouth Ladywood House Express FM 464500 99900 4 79 100 Omni 7D 194.064 SS_South_521 S5_CR002 Portsmouth Havant Havant Angel Radio 472593 106983 14 30 30 Omni 7D 194.064 SS_South_523 S12_AL146H Petersfield Hindhead Hindhead The Breeze 488600 135600 242 15 100 Dir 9C 206.352 SS_South_1224 S12_AL145A Petersfield Haslemere Haslemere The Breeze 488500 133150 169 30 100 Dir 9C 206.352 SS_South_1225 S12_AL146P Petersfield Petersfield Petersfield The Breeze 474800 123300 61 20 100 Omni 9C 206.352 SS_South_1226 S12_AL146F Petersfield Four_Marks Four Marks The Breeze 466500 136600 214 16 100 Dir 9C 206.352 SS_South_1227 S12_AL146L Petersfield Alton I Brockham Hill The Breeze 472300 142800 211 28 100 Dir 9C 206.352 SS_South_12


43


Site Hgt m a.s.l.



29 S6_AL182M Chichester Midhurst Midhurst Spirit FM 491100 125000 180 81 100 Dir 8B 197.648 SS_South_630 S6_AL182C Chichester Chichester The Trundle Spirit FM 487600 111100 197 30 100 Dir 8B 197.648 SS_South_631 S6_AL182L Chichester Littlehampton Hammerpot Spirit FM 507190 105483 36 21 100 Dir 8B 197.648 SS_South_633 S15_CR210 Guildford Farnborough Farnborough BGWS 486100 157300 62 10 100 Omni 7D 194.064 SS_South_1534 S15_CR096 Guildford Aldershot Aldershot BFBS 486400 151200 100 20 100 Omni 7D 194.064 SS_South_1535 S15_CR220 Guildford Guildford Hoggs Back Kane FM 497500 148600 138 30 100 Omni 7D 194.064 SS_South_1537 S11_AL212 Basingstoke Basingstoke Fanum House The Breeze 464900 152701 87 88 100 Dir 8B 197.648 SS_South_11

38 S14_AL273 Reading ReadingPark Royal Water Tower Jack FM 466450 172900 100 48 100 Omni 9B 204.64 SS_South_14

39 S14_CR214 Reading Reading Reading One Ummah FM 474000 172500 58 20 100 Dir 9B 204.64 SS_South_1441 S13_AL193 Oxford Oxford Boars Hill Jack FM 448250 203000 162 51 100 Dir 8A 195.936 SS_South_13

43 S24_AL159 Aylesbury Aylesbury Quainton Hill Mix 96 474993 221273 183 40 100 Dir 9A 202.928 SS_South_24Better site serving Aylesbury 'indoors' needed

44 S23_CR208Marlow & High Wyk High Wycombe High Wycombe

High Wycombe_CR 485039 192646 145 38 100 Dir 9C 206.352 SS_South_23

45 S23_CR209Marlow & High Wyk Marlow Handy Cross Fm Marlow FM 486000 185700 27 15 100 Dir 9C 206.352 SS_South_23

47 S47_AL299 Banbury Banbury Farthinghoe Touch FM 453350 238700 156 46 100 Omni 8B 197.648 SS_South_47Extra site serving Banbury 'indoors' needed Zycomm BS

48 S25_AL148 West London Slough Slough Time 106 495391 181377 34 110 100 Omni 8A 195.936 SS_South_2550 S25_CR217 West London Egham Egham INSANITY 499800 170700 53 15 100 Omni 8A 195.936 SS_South_2551 S25_CR073 West London Hayes St. Anselms Hayes FM 509800 179600 32 40 100 Omni 8A 195.936 SS_South_2552 S25_CR061 West London West_London Glade Lane Desi Radio 513989 179577 27 42 50 Dir 8A 195.936 SS_South_2555 S17_CR223 Reigate Reigate Reigate Susy Radio 525800 152100 221 15 100 Dir 9A 202.928 SS_South_1756 S16_CR206 East Grinstead East Grinstead East Grinstead Meridian FM 539786 138480 131 16 100 Omni 8A 195.936 SS_South_1657 S8_AL263H Haywards Heath Haywards Heath Haywards Heath Bright FM 533800 122950 77 35 100 Omni 9B 204.64 SS_South_858 S8_AL263L Haywards Heath Lewes Lewes County Bright FM 540800 109900 25 26 100 Dir 9B 204.64 SS_South_859 S8_CR207 Haywards Heath Uckfield Uckfield Uckfield FM 548300 120700 35 17 100 Omni 9B 204.64 SS_South_8

60 S9_AL206Hastings & Eastbourne Eastbourne Butt's Brow Sovereign Radio 558000 101500 184 20 100 Dir 7D 194.064 SS_South_9

61 S9_AL210Hastings & Eastbourne Hastings Hastings Arrow FM 580701 110000 70 39 100 Dir 7D 194.064 SS_South_9

62 S9_COMBHastings & Eastbourne

Hastings & Eastbourne

Hastings & Eastbourne Arrow FM 571100 105400 0 15 100 Dir 7D 194.064 SS_South_9

63 S8_COMB Haywards Heath Haywards Heath S8_Comb S8_Comb 541250 119650 20 15 100 Dir 9B 204.64 SS_South_864 S7_AL278 Brighton Worthing Guildbourne Splash FM 514900 102700 4 32 100 Dir 9A 202.928 SS_South_765 S7_CR211 Brighton Seahaven Newhaven Fort Seahaven FM 544600 100100 49 20 100 Dir 9A 202.928 SS_South_767 S7_CR057W Brighton Brighton Whitehawk Hill Radio Reverb 533000 104500 111 32 100 Dir 9A 202.928 SS_South_7


44


Site Hgt m a.s.l.



69 S27_AL170 St Albans ST Albans Hemel Hempsted Heart 508800 204400 140 40 100 Dir 9A 202.928 SS_South_2770 S27_CR090 St Albans St Albans St Albans Radio Verulan 515000 207600 119 30 100 Dir 9A 202.928 SS_South_2771 S27_CR216 St Albans Watford Watford The Vibe 511000 196500 74 54 100 Dir 9A 202.928 SS_South_2772 S28_AL259L Hertfordshire Letchworth Letchworth Bob FM 520850 231350 95 10 100 Dir 7D 194.064 SS_South_28 Zycomm BS73 S28_AL259S Hertfordshire Stevenage Old Knebworth Bob FM 523100 220800 121 23 100 Dir 7D 194.064 SS_South_28 Zycomm BS74 S28_AL259H Hertfordshire Hertford Cole Green Bob FM 528700 211550 68 20 100 Dir 7D 194.064 SS_South_28 Zycomm BS

77 S26_CR198 Luton Luton Luton Inspire FM 507500 221100 172 45 100 Dir 8B 197.648 SS_South_2610dB restriction NW may mitigate PMR Zycomm BS

78 S36_CR200 Biggleswade Bedford Bedford In2beats FM 504500 251600 76 33 100 Omni 8A 195.936 SS_South_3610dB restriction NW may mitigate PMR Zycomm BS

79 S36_CR196 BiggleswadeBiggleswade & Sandy Potton Biggles FM 521600 249000 46 30 100 Dir 8A 195.936 SS_South_36 Zycomm BS

81 LNW_CR068London Northwest Harlesden Stonebridge Bang Radio 520700 183900 33 28 100 Omni 9B 204.64 SS_South_LNW

82 LNW_CR073London Northwest Hayes

St. Anselms Church London NW 509800 179600 32 40 100 Dir 9B 204.64 SS_South_LNW

83 LNW_DL011HLondon Northwest Harrow Harrow Weald London NW 513889 192876 126 45 100 Dir 9B 204.64 SS_South_LNW

84 LNW_DL011ALondon Northwest Arkley Arkley London NW 522088 195775 142 30 100 Dir 9B 204.64 SS_South_LNW

85 LNW_DL011MLondon Northwest Hampstead Hampstead London NW 526025 186250 115 30 100 Dir 9B 204.64 SS_South_LNW

87 LNE_AL175 London Northeast Walthamstow Lea Bridge Rd Sunrise radio 535987 186576 4 15 100 Omni 8A 195.936 SS_South_LNE

88 LNE_AL200L London Northeast Haringey Alexandra PalaceLondon Greek Radio 529550 190050 90 97 100 Dir 8A 195.936 SS_South_LNE

89 LNE_CR069 London Northeast Newham Forest Gate Nusoundradio 540400 185200 10 19 100 Omni 8A 195.936 SS_South_LNE

91 LNE_CR007X London Northeast Goodmayes Goodmayes Ex Radio Ummah 546286 187176 13 15 100 Omni 8A 195.936 SS_South_LNE

92 LNE_CR007X London Northeast Chingford South New New 540438 192888 69 15 100 Omni 8A 195.936 SS_South_LNE

93 LNE_CR007X London Northeast High Beach ching Ex Radio Ummah 539513 197075 92 30 100 Dir 8A 195.936 SS_South_LNE


45


Site Hgt m a.s.l.

Antenna Hgt m ERP W Omni/Dir Block


95 LNW_CR074XLondon Northwest Hammersmith Hammersmith OnFM 523200 178600 2 54 100 Dir 9B 204.64 SS_South_LNW

96 LNW_CR074XLondon Northwest Ealing Ealing Archive Svc 517189 180577 29 63 100 Dir 9B 204.64 SS_South_LNW

97 LNW_DL011London Northwest Hendon Hendon London II site 521488 188576 50 50 100 Omni 9B 204.64 SS_South_LNW

98 LSW_AL191London Southwest Kingston Tolworth Tower

107.8 Radio Jackie 519800 165900 27 75 100 Omni 8B 197.648 SS_South_LSW

99 LSW_AL176HLondon Southwest Heathrow Heathrow Premier 507890 177277 27 42 100 Dir 8B 197.648 SS_South_LSW

100 LSW_DL011RLondon Southwest Richmond Richmond London II 518389 173877 40 19 100 Omni 8B 197.648 SS_South_LSW

103 LSW_DM001ELondon Southwest Esher Esher TE National DAB I 514989 163778 29 20 100 Omni 8B 197.648 SS_South_LSW

104 LSW_NEW2London Southwest

Walton on Thames

Walton on Thames

Walton on Thames 511900 167250 23 25 100 Omni 8B 197.648 SS_South_LSW

105 LSW_NEW3London Southwest Sutton Sutton New 3 527000 164050 66 25 100 Omni 8B 197.648 SS_South_LSW

106 LSW_NEW4London Southwest Wimbledon Wimbledon New 4 525050 172025 40 25 100 Omni 8B 197.648 SS_South_LSW

108 LSE_AL173 London Southeast Crystal Palace London London 533950 171150 100 149 100 Dir 9C 206.352 SS_South_LSE109 LSE_CR077X London Southeast Bexley London London 550285 178477 21 30 100 Omni 9C 206.352 SS_South_LSE110 LSE_DM001X London Southeast Sidcup Sidcup London 546186 171777 62 30 100 Omni 9C 206.352 SS_South_LSE111 LSE_WOO London Southeast Woolwich Woolwich TV Site 546000 179400 4 30 100 Omni 9C 206.352 SS_South_LSE112 LSE_AL176D London Southeast Dartford Dartford Premier 555285 176877 1 36 100 Dir 9C 206.352 SS_South_LSE113 LSE_OPR London Southeast Orpington Orpington TV Site 545800 165300 73 35 100 Omni 9C 206.352 SS_South_LSE115 LCE_CR060 Cental London Cental London Guys Hospital Resonance fm 532900 180000 2 95 100 Omni 7D 194.064 SS_South_LCS116 LCE_WOR Cental London Cental London Worlds End TV Site 526400 177400 2 60 100 Omni 7D 194.064 SS_South_LCS118 S21_CR201 Ashford Ashford William Harvey AHBS Community 604100 142100 62 37 100 Omni 9A 202.928 SS_South_21

119 S19_CR203 Folkestone Folkestone Folkestone AcademyFM 621800 137300 43 20 100 Omni 9C 206.352 SS_South_19Coverage needs extending to Dover ?

120 S18_CR202 Ramsgate Ramsgate Thanet Academy FM 636300 166600 49 25 100 Omni 7D 194.064 SS_South_18121 S20_CR066 Cantebury Cantebury Eliot College CSR 614100 159600 60 20 100 Omni 9B 204.64 SS_South_20122 S22_CR204 Gillingham Gillingham Gillingham Radio Sunlight 578000 166800 88 25 100 Omni 8A 195.936 SS_South_22123 S22_CR219 Gillingham Sittingbourne Sittingbourne SFM 590600 163700 20 20 100 Omni 8A 195.936 SS_South_22124 S22_CR107 Gillingham Sheppy Sheppy BRFM Bridge 596800 173300 49 30 100 Omni 8A 195.936 SS_South_22126 S34_CR075 Basildon Brentwood Brentwood Phoenix FM 559200 195400 79 20 100 Omni 9B 204.64 SS_South_34127 S34_CR218 Basildon Basildon Southernhay Gateway FM 570700 188400 30 42 100 Omni 9B 204.64 SS_South_34


46


Site Hgt m a.s.l.



129 S35_AL313X Southend Southend Southend Southend FM 588200 185700 24 58 100 Dir 9C 206.352 SS_South_35130 S33_AL221X Chelmsford Chelmsford Church Green Dream 107.7 577883 204975 104 30 100 Omni 8B 197.648 SS_South_33

131 S33_CR106 ChelmsfordBurnham-on-Crouch Mayland Hill Saint FM 592281 200275 39 20 100 Omni 8B 197.648 SS_South_33

1 E31_AL128 Tendring Tendring Clackton Dream 100 FM 618279 216274 6 43 100 Dir 9C 206.352 SS_East_31

2 E30_CR190 Felixstowe Felixstowe Felixstowe Felixstowe Radio 630278 235072 22 14 100 Dir 8B 197.648 SS_East_303 E32_CR195 Colchester Coggeshall Pattiswick Leisure FM 581382 224073 63 22 100 Omni 8A 195.936 SS_East_32

4 E32_CR058 Colchester ColchesterColchester Garrison BFBS 598900 224200 33 16 100 Omni 8A 195.936 SS_East_32

Extra site serving Braintree needed

5 E29_AL308 Ipswich Ipswich Warren Heath Town 102 619579 242471 33 45 100 Dir 7D 194.064 SS_East_29

6 E29_CR087 Ipswich IpswichChantry High School

Ipswich Community Radio 614579 243171 45 13 100 Omni 7D 194.064 SS_East_29

7 E37_AL194C Cambridge & Ely Cambridge Gog Magog STAR FM 549085 253270 69 29 100 Omni 8B 197.648 SS_East_37 Zycomm BS8 E37_AL194E Cambridge & Ely Ely Ely Cathedral Star FM 554085 280068 13 66 100 Omni 8B 197.648 SS_East_37 Zycomm BS

9 E37_CR193 Cambridge & Ely Cambridge University Library CAM FM 544086 258370 8 48 100 Omni 8B 197.648 SS_East_37 Zycomm BS14 E45_CR199 Godmanchester Godmanchester Huntingdon HCR 524788 272569 18 28 100 Omni 9A 202.928 SS_East_45 Zycomm Mob

15 E43_CR191 Forest Heath Forest HeathMildenhall St Mary's Chu Zack FM 571000 274600 8 43 100 Omni 9B 204.64 SS_East_43

16 E38_CR189 Bury St Edmunds Bury St Edmunds Bury St Edmunds RWS 585000 262700 59 31 100 Omni 9A 202.928 SS_East_38

17 E39_CR188 Southwold Southwold ReydonBlyth Valley radio 648976 276968 10 10 100 Dir 9B 204.64 SS_East_39

18 E40_AL300 Norwich Norwich Stoke Holy Cross Norwich Radio 625778 302566 67 105 100 Omni 9C 206.352 SS_East_4019 E40_CR192 Norwich Norwich Markham Tower Future FM 621278 310866 22 63 100 Omni 9C 206.352 SS_East_40

21 E42_AL134 Kings Lynn Kings LynnGreat Massingham KLFM 96.7 578783 322865 92 45 100 Omni 8A 195.936 SS_East_42 Zycomm BS

22 E42_NEW Kings Lynn Kings Lynn New New 565150 320650 12 20 100 Omni 8A 195.936 SS_East_42New site added to serve Kings Lynn Zycomm BS

24 E41_AL285B North Norfolk North Norfolk Bunkers HillNorth Norfolk Radio 590281 338763 71 30 100 Omni 7D 194.064 SS_East_41 Zycomm BS

25 E41_AL285F North Norfolk North Norfolk FakenhamNorth Norfolk Radio 592581 330164 51 20 100 Omni 7D 194.064 SS_East_41 Zycomm BS

26 E41_AL285S North Norfolk North Norfolk Stody North Norfolk Radio 607280 333264 61 40 100 Omni 7D 194.064 SS_East_41 Zycomm BS

27 E41_AL285A North Norfolk North Norfolk AylmertonNorth Norfolk Radio 615400 339100 87 33 100 Omni 7D 194.064 SS_East_41 Zycomm BS


47


Site Hgt m a.s.l.



1 M49_AL330 Coventry CoventrySamuel Vale House Touch FM 433150 279700 91 58 100 Omni 8B 197.648 SS_Mid_49 Zycomm BS

4 M48_AL309Stratford & Warwick Warwick Leamington Spa Touch Radio 432900 266450 90 39 100 Dir 9B 204.64 SS_Mid_48 Zycomm Mob

5 M48_AL185Stratford & Warwick Stratford Lark Stoke Touch 418700 242600 257 12 100 Omni 9B 204.64 SS_Mid_48 Zycomm Mob

6 M48_NEWStratford & Warwick Stratford Stratford New 420450 255100 35 24 100 Omni 9B 204.64 SS_Mid_48 Zycomm Mob

8 M50_AL331 Rugby RugbyRoyal Court Rounds Garde Rugby FM 449950 275500 108 45 100 Omni 8A 195.936 SS_Mid_50 Zycomm BS

11 M62_CR039 Birmingham East Birmingham East Birmingham East Unity FM 408300 285600 123 60 100 Omni 9A 202.928 SS_Mid_62 Zycomm Mob12 M62_CR174 Birmingham East Castle Vale Castle Vale Vale FM 414000 291400 88 40 100 Omni 9A 202.928 SS_Mid_62 Zycomm Mob

13 M61_CR177 West_BromwichSandwell & West Bromwich Sandwel Raaj FM 400800 290800 161 50 100 Omni 8A 195.936 SS_Mid_61 Zycomm BS

14 M61_CR041 West_Bromwich Stourbridge Brierley Hill The 'Bridge 391601 286768 149 45 100 Omni 8A 195.936 SS_Mid_61 Zycomm BS

17 M60_AL199Walsall & Wolverhampton Wolverhampton Mander House Signal 107 391501 298567 155 53 100 Omni 9C 206.352 SS_Mid_60 Zycomm Mob

19 M60_CR175XWalsall & Wolverhampton Walsall Walsall Ambur Radio 401100 298667 121 48 100 Omni 9C 206.352 SS_Mid_60 Zycomm Mob

21 M58_CR053 Worcester Worcester Worcester

Youth Community Radio 386800 255100 72 18 100 Omni 7D 194.064 SS_Mid_58

22 M46_CR184 Northampton NorthamptonUniversity of Northampto Insperation FM 476200 264300 121 17 100 Omni 9C 206.352 SS_Mid_46 Zycomm Mob

23 M51_CR013Corby & Harborough

Market Harborough

Little Oxendon Farm Harborough FM 472700 284000 153 35 100 Omni 7D 194.064 SS_Mid_51 Zycomm BS

24 M51_CR185Corby & Harborough Corby Corby Corby Radio 488100 288500 115 35 100 Omni 7D 194.064 SS_Mid_51 Zycomm BS

26 M54_AL231 Hinckley Hinckley Barwell Oak FM 445350 297000 118 30 100 Omni 9C 206.352 SS_Mid_54 Zycomm Mob27 M55_CR010 Leicester Leicester Gorse Hill Farm Take Over Radio 456900 306200 79 6 100 Omni 9A 202.928 SS_Mid_55 Zycomm Mob28 M55_CR178 Leicester Leicester Central Leicester EAVA FM 459200 306300 52 30 100 Omni 9A 202.928 SS_Mid_55 Zycomm Mob30 M55_CR179 Leicester Leicester Leicester Demon FM 458200 303800 56 48 100 Omni 9A 202.928 SS_Mid_55 Zycomm Mob

32 M66_AL230 Loughborough LoughboroughLoughborough University Oak FM 452400 319000 50 68 100 Dir 8A 195.936 SS_Mid_66 Zycomm BS

33 M65_CR012 Vale of Belvoir Vale of BelvoirWhite Lodge Farm The Eye 472100 323800 167 20 100 Omni 8B 197.648 SS_Mid_65 Zycomm BS

34 M67_CR181 Coalville Coalville Hoo Ash Farm Hermitage FM 440800 314900 161 14 100 Omni 9B 204.64 SS_Mid_67 Zycomm Mob35 M64_CR011 Derby Derby Normanton Radio Iklhas 433500 334500 94 15 100 Omni 9A 202.928 SS_Mid_64 Zycomm Mob


48


Site Hgt m a.s.l.



36 M63_AL217L South StaffsSoutheast Staffordshire Lichfield Touch FM 416398 304266 149 100 100 Dir 7D 194.064 SS_Mid_63 Zycomm BS

37 M63_AL217B South StaffsSoutheast Staffordshire Burton Touch FM 426597 322665 122 30 100 Omni 7D 194.064 SS_Mid_63 Zycomm BS

40 M52_AL229R Rutland RutlandBurley Water Tower Rutland FM 489191 311166 144 27 100 Dir 9B 204.64 SS_Mid_52 Zycomm Mob

41 M52_AL229S Rutland StamfordNew Stamford College Rutland FM 503490 307766 41 25 100 Omni 9B 204.64 SS_Mid_52 Zycomm Mob

43 M53_CR172 Spalding Spalding Fulney Tulip Radio 526588 322265 4 32 100 Omni 9C 206.352 SS_Mid_5344 M68_CR168 Grantham Grantham Springfield Road Gravity FM 490891 334664 62 52 100 Omni 7D 194.064 SS_Mid_68 Zycomm BS

45 M57_AL138 Ludlow Ludlow Woofferton Sunshine Radio 351105 269069 79 105 100 Omni 8B 197.648 SS_Mid_57Need site near to Ludlow rather than MF site

47 M59_CR1005 Staffordshire Stafford Stafford Stafford FM 392001 323265 76 20 100 Omni 9B 204.64 SS_Mid_59 Zycomm Mob48 M59_CR1052 Staffordshire Newport Newport Newport CR 374403 319165 70 16 100 Omni 9B 204.64 SS_Mid_59 Zycomm Mob

1 NW6_AL237Shewsbury & Telford Telford Heath Hill Telford FM 368100 307703 192 42 50 Dir 9A 202.928 SS_NW_6 Zycomm Mob

2 NW6_AL310Shewsbury & Telford Shewsbury Shelton Signal_107 346505 313465 90 27 100 Dir 9A 202.928 SS_NW_6 Zycomm Mob

4 NW5_CR091 Wrexham Wrexham Wrexham Calon FM 332600 351100 86 19 100 Omni 8A 195.936 SS_NW_55 NW1_CR245 Anglesey Anglesey Cwalchmai Mon FM 238955 376737 85 35 100 Omni 9C 206.352 SS_NW_1 Merseyside Mob6 NW2_CR156 Llandudno Llandudno Llandudno Tudno FM 278512 381560 5 26 100 Dir 9B 204.64 SS_NW_2 Merseyside Mob7 NW3_CR157 Glan Clwyd_Rhyl Rhyl Rhyl Point FM 300500 381100 1 17 100 Dir 8A 195.936 SS_NW_38 NW3_CR244 Glan Clwyd_Rhyl Glan Clwyd Glan Clwyd Hosp Glan Clwyd AM 300300 376000 11 10 100 Omni 8A 195.936 SS_NW_310 NW17_AL267 Lakeland Windermere Windermere Lakeland Radio 338300 498003 222 30 100 Dir 9C 206.352 SS_NW_17 Merseyside Mob11 NW17_AL267 Lakeland Kendal Kendal Lakland Radio 354000 491300 172 44 100 Dir 9C 206.352 SS_NW_17 Merseyside Mob

13 NW16_AL147Lancaster & Morecambe Morecambe Bay Morecambe Bay The Bay 323950 479250 254 68 100 Dir 7D 194.064 SS_NW_16

14 NW16_CR213Lancaster & Morecambe Morecambe Bay Morecambe Bay Barrow CR 319808 469052 10 15 100 Omni 7D 194.064 SS_NW_16

15 NW16_CRNEWLancaster & Morecambe

Lancaster_Morecambe

Lancaster_Morecambe Barrow CR 349033 466417 81 20 100 Omni 7D 194.064 SS_NW_16

New site added to serve Morecambe. Need site for Lancaster

17 NW15_CR051 South Cumbria South Cumbria Kirkby Lonsdale Indigo Radio 361100 478500 68 12 100 Omni 8B 197.648 SS_NW_1518 NW14_AL137 Blackpool Blackpool Blackpool Tower The Wave 96.5 330600 436050 9 135 100 Dir 9B 204.64 SS_NW_14 Merseyside Mob19 NW13_CR158 Preston Preston Preston Preston FM 354200 429100 32 55 100 Omni 9A 202.928 SS_NW_1321 NW12_AL292 East Lancashire Blackburn Blackburn The Bee 369550 426750 198 34 100 Dir 8A 195.936 SS_NW_1222 NW12_AL183 East Lancashire East Lancs Haslingden Asian Sound 379550 423600 341 43 50 Dir 8A 195.936 SS_NW_1223 NW12_AL258 East Lancashire Burnley Pendle Forest 2BR 382500 438403 273 35 50 Dir 8A 195.936 SS_NW_1224 NW12_CR099 East Lancashire Nelson Brierfields Pendle CR 386101 436155 262 23 100 Omni 8A 195.936 SS_NW_1225 NW10_CR025 Chorley Chorley Chorley Chorley FM 358404 417357 86 30 100 Omni 8B 197.648 SS_NW_1029 NW11_AL234 Bolton Bolton Tottington Tower FM 376300 412104 224 25 100 Dir 9C 206.352 SS_NW_11 Merseyside Mob


49


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30 NW9_AL189 Wigan Wigan Billinge Hill Wish 102 352300 401604 169 30 100 Dir 8A 195.936 SS_NW_9Not seving Wigan 'indoor' but good area coverage

31 NW7_CR162 Knowsley Knowsley Knowsley KCC 344205 390759 31 57 100 Omni 9A 202.928 SS_NW_732 NW8_CR102H Warrington Halton Halton Halton CR 353700 381900 79 10 100 Omni 9B 204.64 SS_NW_8 Merseyside Mob

33 NW8_AL214 Warrington WarringtonHigh Warren Reservoir Wire FM 361450 384300 86 14 100 Omni 9B 204.64 SS_NW_8 Merseyside Mob

34 NW8_CR137 Warrington Warrington Warrington Radio Warrington 358450 385900 6 14 100 Omni 9B 204.64 SS_NW_8 Need SB III Block ! Merseyside Mob

36 NW4_CR100 Wirral WirralBidston Lighthouse Wirral Radio 328000 387100 20 46 100 Omni 9C 206.352 SS_NW_4 Merseyside Mob

37 NW4_CR155 Wirral Wirral Willaston Flame CR 332800 377017 50 10 100 Omni 9C 206.352 SS_NW_4 Merseyside Mob

39 NW81_CR035 Manchester_West SalfordSwinton Civic Centre Salford CR 377500 401600 63 30 25 Omni 8B 197.648 SS_NW_81

40 NW81_CR187 Manchester_West Manchester Portland Tower Unity radio 384200 397900 40 85 25 Omni 8B 197.648 SS_NW_81

42 NW81_CR023 Manchester_West Manchester Longsight All FM 387500 395100 54 40 25 Omni 8B 197.648 SS_NW_81

45 NW83_CR033 Tameside Tameside Harrop Edge

Tameside Community Radio 398400 396400 299 10 50 Dir 9C 206.352 SS_NW_83 Need SB III Block ! Merseyside Mob

46 NW82_CR235 Manchester North Oldham The Civic Centre

ldham Community Radio 392300 405100 201 65 100 Omni 9B 204.64 SS_NW_82 Merseyside Mob

47 NW82_CR165 Manchester NorthManchester North Maston

North Manchester FM 386700 401700 80 40 100 Omni 9B 204.64 SS_NW_82 Merseyside Mob

48 NW82_AL183 Manchester NorthManchester North Ashton Moss Asian Sound 392501 399358 101 40 100 Omni 9B 204.64 SS_NW_82 Merseyside Mob

50 NW84_CR034 Manchester South Stockport Ratcliffe Towers Pure FM 387700 388400 51 25 100 Omni 9A 202.928 SS_NW_84

51 NW84_CR024 Manchester SouthManchester South Wythenshawe

Wythenshawe FM 382700 387100 59 30 100 Omni 9A 202.928 SS_NW_84

53 NW17_CR267 Lakeland Keswick Keswick Forest Lakeland Radio 322350 524400 202 18 100 Dir 9C 206.352 SS_NW_17 Merseyside Mob54 NW18_CR181 Penrith Penrith Penrith Eden Radio 350905 529347 148 30 100 Omni 9B 204.64 SS_NW_18

1 N1_CR148 Sutton-in-Craven Sutton-in-Craven Sutton-in-Craven Drystone Radio 401300 443354 270 20 100 Omni 7D 194.064 SS_North_1 Zycomm BS2 N8_CR026 Rochdale Rochdale Stoneyfield Crescent Radio 389600 412600 142 20 100 Omni 7D 194.064 SS_North_83 N17_CR160 Macclesfield Macclesfield Bollington The Thread 393400 378100 150 34 100 Dir 7D 194.064 SS_North_174 N17_AL213 Macclesfield Macclesfield Sutton Common Silk FM 393400 367750 400 5 100 Dir 7D 194.064 SS_North_17

6 N18_CR1013Crewe & Nantwiche

Crewe & Nantwiche Crewe The Cat 369603 354662 51 26 100 Omni 8B 197.648 SS_North_18

7 N19_CR161 Stoke-On-Trent Biddulph Rails Farm Moorlands Radio 391500 358500 325 20 100 Dir 9C 206.352 SS_North_19 Merseyside Mob

8 N19_CR003 Stoke-On-Trent Stoke On Trent Stoke on TrentCross Rhythms City Radio 391800 349650 211 30 100 Omni 9C 206.352 SS_North_19 Merseyside Mob

9 N19_CR003 Stoke-On-Trent Stoke On Trent Stoke on TrentCross Rhythms City Radio 381102 347962 207 18 100 Omni 9C 206.352 SS_North_19 Merseyside Mob


50


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11 N16_AL286B High Peak High Peak Buxton High Peak Radio 405850 375300 429 22 100 Omni 9B 204.64 SS_North_16Zycomm & Merseyside Mob

12 N16_AL286C High Peak High PeakChapel-en-le-Frith High Peak Radio 406200 380800 221 10 100 Omni 9B 204.64 SS_North_16

Zycomm & Merseyside Mob

13 N16_AL286H High Peak High Peak Hope Valley High Peak Radio 417700 384204 217 15 100 Omni 9B 204.64 SS_North_16Zycomm & Merseyside Mob

14 N16_AL286U High Peak High Peak Buxworth High Peak Radio 402600 383304 288 25 100 Dir 9B 204.64 SS_North_16Zycomm & Merseyside Mob

16 N26_CR015 Nottingham Nottingham Mapperley Dawn FM 458200 342800 120 20 100 Omni 9C 206.352 SS_North_2617 N26_CR171 Nottingham Ilkeston Ilkeston Erewash Sound 446400 341600 93 28 100 Omni 9C 206.352 SS_North_2618 N26_CR016 Nottingham Nottingham Nottingham Kemet Radio 455700 340600 52 63 100 Dir 9C 206.352 SS_North_2620 N21_AL286A High Peak Ashbourne Ashbourne High Peak Radio 418150 347350 162 15 100 Omni 9B 204.64 SS_North_21 Zycomm Mob21 N21_AL286W High Peak Wirksworth Hardhurst Fm High Peak Radio 429697 352862 241 10 100 Omni 9B 204.64 SS_North_21 Zycomm Mob

22 N21_CR170 High Peak Ripley RipleyAmber Sounds FM 440000 350300 155 34 100 Omni 9B 204.64 SS_North_21 Zycomm Mob

24 N22_AL226 Mansfield Mansfield Fishpond Hill Mansfield 103.2 451150 360650 172 46 100 Dir 7D 194.064 SS_North_22 Zycomm BS

26 N20_AL227CChesterfield & Matlock Chesterfield Chesterfield Peak 107 FM 438200 376404 145 43 100 Dir 8B 197.648 SS_North_20 Zycomm BS

27 N20_AL227MChesterfield & Matlock Chesterfield Chesterfield Peak 107 FM 424598 363661 305 45 100 Omni 8B 197.648 SS_North_20 Zycomm BS

29 N24_CR523 Newark Newark Newark Radio Newark 480792 353162 17 10 100 Omni 9B 204.64 SS_North_24 Zycomm Mob

31 N23_CR166 Lincoln Lincoln Lincoln CathedralLincoln City Radio 497690 371760 60 85 100 Omni 9A 202.928 SS_North_23 Zycomm Mob

32 N25_CR530 Boston Boston Boston Endeavour FM 532687 344263 1 25 50 Dir 8B 197.648 SS_North_25 Zycomm BS34 N13_AL224X Rother Valley Worksop Worksop TRAX FM 459494 377460 68 20 100 Dir 9C 206.352 SS_North_1335 N13_AL224D Rother Valley Doncaster Clifton TRAX FM 451900 395950 135 36 100 Dir 9C 206.352 SS_North_1336 N13_CR150 Rother Valley Doncaster Doncaster Sine FM 457700 403000 16 27 100 Omni 9C 206.352 SS_North_1337 N13_CR151 Rother Valley Rother Valley Wales Redroad FM 447700 382600 120 20 100 Omni 9C 206.352 SS_North_1340 N14_AL314 Rotherham Rotherham Rotherham Rother FM 443250 391300 116 53 100 Dir 9A 202.928 SS_North_14 Zycomm Mob42 N15_CR083 Sheffield West Sheffield West Tapton Hill Sheffield Live! 432400 387000 230 28 100 Omni 8A 195.936 SS_North_15 Zycomm BS43 N7_AL280A Barnsley Barnsley Ardsley Dearne FM 439000 406104 94 44 100 Omni 7D 194.064 SS_North_7 Zycomm BS44 N7_AL280P Barnsley Barnsley Ardsley Dearne FM 425897 404458 269 15 100 Omni 7D 194.064 SS_North_7 Zycomm BS

46 N9_CR154 Thorne_MoorendsThorne_Moorends Thorne TMCR 468500 413400 2 15 100 Omni 9B 204.64 SS_North_9 Zycomm Mob

47 N5_AL242 West Yorks South Wakefield Birkwood Farm Ridings FM 436097 423356 35 19 100 Dir 8B 197.648 SS_North_5 Zycomm BS48 N5_CR085 West Yorks South Dewsbury Dewsbury Branch FM 425200 423000 133 12 100 Omni 8B 197.648 SS_North_5 Zycomm BS49 N5_CR022 West Yorks South Halifax Halifax Phoenix FM 410300 424200 245 40 100 Omni 8B 197.648 SS_North_5 Zycomm BS50 N5_CR136Y West Yorks South Huddersfield Ainley Top Huddersfield CR 412399 419656 246 67 100 Omni 8B 197.648 SS_North_5 Zycomm BS


51


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52 N2_CR021 Bradford Bradford Idle BCB 416400 437400 216 43 100 Dir 9A 202.928 SS_North_2 Zycomm Mob

54 N3_CR031 Leeds LeedsPotternewton Lane Asian fever 430200 436600 107 52 100 Omni 9C 206.352 SS_North_3

55 N4_CR064 Wetherby Wetherby Collingham Tempo 107.4 438500 444700 94 10 100 Omni 8A 195.936 SS_North_4 Zycomm BS

56 N6_CR152 East Yorks Market Weighton Market Weighton Vixen FM 490300 442100 120 27 100 Omni 9A 202.928 SS_North_6 Zycomm Mob

57 N6_CR133Y East Yorks Pocklington PocklingtonWest Wolds Radio 480292 448954 35 14 100 Omni 9A 202.928 SS_North_6 Zycomm Mob

58 N6_CR138Y East Yorks Beverley Beverley Beverley FM 501990 440254 31 16 100 Omni 9A 202.928 SS_North_6 Zycomm Mob

60 N10_AL315 Hull HullHumber Bridge - North Pi KCFM 502300 425300 0 164 100 Dir 8B 197.648 SS_North_10 Zycomm BS

61 N10_CR056 Hull West HullHull Royal Infirmary

West Hull Community Radi 508400 428700 2 65 100 Omni 8B 197.648 SS_North_10 Zycomm BS

62 N10_CR147Y Hull East Hull Muswell CourtHull Kingston Radio 513289 432355 4 49 100 Omni 8B 197.648 SS_North_10 Zycomm BS

64 N11_CR052 Withernsea Withernsea Withernsea Seaside FM 534187 427956 8 20 100 Dir 8A 195.936 SS_North_11 Zycomm BS65 N12_AL266 Grimsby Grimsby Bevan House Compass FM 527900 410200 4 55 100 Dir 7D 194.064 SS_North_12 Zycomm BS

1 NE5_AL307CThirsk & Northallerton Thirsk Calvert's Carpets Star Radio 442900 481903 30 15 100 Dir 9B 204.64 SS_Northeast_5 Zycomm Mob

2 NE5_307NThirsk & Northallerton North Allerton North Allerton Star Radio 436500 494300 36 43 100 Omni 9B 204.64 SS_Northeast_5 Zycomm Mob

4 NE4_AL181 Catterick CatterickCatterick Garrison BFBS 418100 498400 152 20 50 Dir 8B 197.648 SS_Northeast_4

6 NE6_CR098 Teeside West TeesideStockton_on_Tees Cross Rythms 444200 518800 14 12 100 Omni 9A 202.928 SS_Northeast_6

7 NE6_CR144 Teeside West Middlesborough MiddlesboroughCommunity Voice 450000 519500 7 12 100 Omni 9A 202.928 SS_Northeast_6

8 NE6_CR123 Teeside West RedcarPark Fm Dunsdale Radio Zetland 445200 523400 22 15 100 Omni 9A 202.928 SS_Northeast_6

9 NE6_CR145 Teeside West Hartlepool Hartlepool Radio Hartlepool 451000 531000 9 14 100 Dir 9A 202.928 SS_Northeast_611 NE3_CR082 Teeside East Teesdale Mickleton Radio Teesdale 397400 522000 352 15 100 Omni 7D 194.064 SS_Northeast_3 Zycomm BS12 NE3_CR082 Teeside East Teesdale Barnard Castle Radio Teesdale 405700 517200 192 20 100 Omni 7D 194.064 SS_Northeast_3 Zycomm BS

13 NE3_CR146 Teeside EastSouthwest Durham High Etherley Bishop FM 416300 528100 200 10 100 Dir 7D 194.064 SS_Northeast_3 Zycomm BS

14 NE3_AL181 Teeside East Darlington Darlington Star Radio 428350 518900 82 38 100 Dir 7D 194.064 SS_Northeast_3 Zycomm BS17 NE8_AL297B Durham Durham Burnhope Star Radio 418300 547650 238 125 50 Dir 9C 206.352 SS_Northeast_818 NE7_AL126 Sunderland Sunderland Haining Sun FM 435500 550903 160 32 100 Omni 8A 195.936 SS_Northeast_7 Zycomm BS

19 NE7_CR143 Sunderland SunderlandMonkswearmouth Spark FM 440000 557900 20 45 100 Dir 8A 195.936 SS_Northeast_7 Zycomm BS

21 NE9_CR050Newcastle & Gateshead Gateshead Gateshead NE1 FM 426600 561500 140 13 100 Omni 9B 204.64 SS_Northeast_9

22 NE9_CR142Newcastle & Gateshead Newcastle West Road Spice FM 422200 564400 105 16 100 Omni 9B 204.64 SS_Northeast_9

24 NE10_CR049 Alnwick Alnwick Alnwick Moor Lionheart CR 417700 612700 133 20 100 Omni 8B 197.648 SS_Northeast_10


52


Site Hgt m a.s.l.



1 SC16_CR080 Edinburgh Leith Leith FM Castle FM 327000 676000 9 60 100 Omni 7D 194.064 SS_Scot_16

2 SC16_CR079 Edinburgh Edinburgh SouthEdinburgh Garrison FM BFBS 322700 668300 162 20 100 Omni 7D 194.064 SS_Scot_16

3 SC16_CR258 Edinburgh Penicuik Penicuik Crystal FM 323750 660250 200 16 100 Omni 7D 194.064 SS_Scot_16

4 SC16_CR081 Edinburgh Midlothian Newton GrangeBlack Diamond FM 334100 662800 158 21 100 Omni 7D 194.064 SS_Scot_16

5 SC16_CR259 Edinburgh Haddington Garleton Hills East Coast FM 351350 676000 176 15 100 Dir 7D 194.064 SS_Scot_16

7 SC15_CR020Stirling & Cumbernauld Cumbernauld Cumbernauld Revival FM 276500 675000 140 71 100 Omni 9A 202.928 SS_Scot_15

8 SC15_AL047Stirling & Cumbernauld Stirling Earls Hill Central FM 272000 688500 422 36 100 Dir 9A 202.928 SS_Scot_15

10 SC13_CR017 Glasgow Glasgow West Glasgow West Insight Radio 254700 668800 27 74 100 Omni 8A 195.936 SS_Scot_1311 SC13_CR018 Glasgow Glasgow Glasgow Sunny Govan 253736 664051 42 60 100 Omni 8A 195.936 SS_Scot_1312 SC13_CR138 Glasgow Barrhead Barrhead Pulse FM 250500 657700 105 20 100 Omni 8A 195.936 SS_Scot_13

14 SC13_CR257 Glasgow Glasgow GlasgowCeltic Music Radio 259514 665635 28 84 100 Dir 8A 195.936 SS_Scot_13

15 SC13_CR256 Glasgow Glasgow GlasgowCeltic Music Radio 261614 661535 36 84 100 Dir 8A 195.936 SS_Scot_13

17 SC11_CR141 Salltcoats & Irvine Saltcoats Saltcoats 3FTM CR 225500 642600 43 3 100 Dir 9C 206.352 SS_Scot_1118 SC11_CR263 Salltcoats & Irvine Irvine Irvine Irvine beat FM 232100 638500 2 50 100 Dir 9C 206.352 SS_Scot_1120 SC12_AL287 Greenock Helensburgh Rosneath Your Radio 225850 681200 103 38 100 Omni 7D 194.064 SS_Scot_12

21 SC12_AL264 Greenock DumbartonDumbarton Castle Your Radio 239101 675401 10 48 100 Omni 7D 194.064 SS_Scot_12

22 SC12_CR124 Greenock Isle of Bute Rothsay Town Bute FM 208919 664435 18 15 100 Omni 7D 194.064 SS_Scot_1223 SC12_CR136 Greenock Dunoon Dunoon Dunoon CR 217218 676934 24 15 100 Omni 7D 194.064 SS_Scot_12

25 SC14_AL251Kintyre Islay & Jura

Kintyre Islay & Jura South Knapdale Argyll FM 183750 674850 447 45 100 Dir 8B 197.648 SS_Scot_14

26 SC27_AL223D Fife Dunfermline Knock Hill Kingdom FM 305400 693702 344 40 100 Dir 8B 197.648 SS_Scot_2727 SC27_AL223K Fife Kirkcaldy Kirkcaldy Kingdom FM 328900 692602 32 50 100 Dir 8B 197.648 SS_Scot_2728 SC27_AL223G Fife Glenrothes Purin Hill Kingdom FM 325200 705902 336 22 100 Omni 8B 197.648 SS_Scot_2729 SC27_AL223F Fife Fife East Neuk Kingdom FM 356800 708800 99 17 100 Omni 8B 197.648 SS_Scot_2730 SC27_AL223A Fife Fife Allanhill Farm Kingdom FM 352000 714102 96 20 100 Dir 8B 197.648 SS_Scot_2733 SC28_AL322 Perth & Pitlochry Perth Kinnoull Hill Heartland FM 312400 723350 15 25 100 Dir 9C 206.352 SS_Scot_2834 SC28_AL113 Perth & Pitlochry Pitlochry Faire Mhor Heartland Radio 299300 758301 481 34 100 Omni 9C 206.352 SS_Scot_28

36 SC29_AL232Dundee & Arbroath Dundee Dundee Law Wave 102 339200 731302 142 12 100 Dir 8A 195.936 SS_Scot_29

37 SC29_AL233ADundee & Arbroath Arbroath Infirmary

Radio North Angus 363400 740402 10 15 100 Dir 8A 195.936 SS_Scot_29

38 SC29_AL233CDundee & Arbroath Carnoustie

Carnoustie High School

Radio North Angus 355404 735029 12 15 100 Dir 8A 195.936 SS_Scot_29

40 SC26_CR262G Nevis Glencoe Glencoe Nevis Radio 226017 751427 719 10 100 Omni 8B 197.648 SS_Scot_2641 SC26_CR262L Nevis Loch Leven Glenachulish Nevis Radio 203419 759027 314 8 100 Omni 8B 197.648 SS_Scot_2642 SC26_CR262F Nevis Fort William Trislaig Nevis Radio 208619 774825 245 15 100 Omni 8B 197.648 SS_Scot_26


53


Site Hgt m a.s.l.



44 SC30_AL187 Oban Oban Pulpit Hill Oban FM 185000 729000 127 25 100 Omni 9B 204.64 SS_Scot_3045 SC25_CR134L Mearns Laurencekirk Laurencekirk Mearns FM 374700 771000 242 25 100 Omni 9C 206.352 SS_Scot_2546 SC25_CR134I Mearns Inverbervie Inverbervie Mearns FM 382800 771700 41 10 100 Dir 9C 206.352 SS_Scot_2547 SC25_CR134S Mearns Stonehaven Stonehaven Mearns FM 387500 784600 68 7 100 Dir 9C 206.352 SS_Scot_2549 SC24_CR028 Aberdeen Aberdeen Aberdeen Shmu 391700 808200 96 48 100 Dir 7D 194.064 SS_Scot_2450 SC22_CR265 Banff & Macduff Banff & Macduff Banff Deveron Radio 368850 864500 15 18 100 Dir 9A 202.928 SS_Scot_2251 SC21_CR264 Moray Moray Tor Sliasg KCR 342506 858018 291 25 100 Omni 8A 195.936 SS_Scot_21

52 SC23_CR133 Aviemore Aviemore Cairngorm Speysound Radio 300500 804800 1109 10 100 Dir 9A 202.928 SS_Scot_2353 SC18_CR262 Skye & Lochalsh Mallaig Cnoc Malagan Nevis Radio 165400 808100 181 25 100 Omni 9C 206.352 SS_Scot_1854 SC18_AL279 Skye & Lochalsh Skye Portree Cuillin FM 148200 844001 42 10 100 Omni 9C 206.352 SS_Scot_1856 SC18_279SC Skye & Lochalsh Skye & Lochalsh Skraig Cuillin FM 145125 840719 372 60 100 Omni 9C 206.352 SS_Scot_1858 SC17_AL202E Isle of Lewis Isle of Lewis Eitshall Isles FM 130627 930411 206 24 100 Omni 7D 194.064 SS_Scot_1759 SC17_AL202N Isle of Lewis Isle of Lewis Ness Isles FM 152624 960909 69 40 100 Omni 7D 194.064 SS_Scot_1761 SC20_AL282S Ullapool Shieldaig Shieldaig Two Lochs Radio 182121 853418 228 12 100 Omni 9B 204.64 SS_Scot_2062 SC20_AL282G Ullapool Gairloch Port Henderson Two Lochs Radio 176322 873917 37 19 100 Omni 9B 204.64 SS_Scot_2063 SC20_AL282L Ullapool Lock Ewe Cliff Hill Two Lochs Radio 185021 879816 179 18 100 Omni 9B 204.64 SS_Scot_2064 SC20_AL282B Ullapool Badcaul Badcaul Two Lochs Radio 198920 892215 234 15 100 Omni 9B 204.64 SS_Scot_2065 SC20_AL198U Ullapool Ullapool Ullapool Lochbroom FM 214218 893415 101 20 100 Omni 9B 204.64 SS_Scot_2066 SC20_AL198P Ullapool Ullapool Polbain Lochbroom 199920 910813 149 25 100 Omni 9B 204.64 SS_Scot_2068 SC19_CR254M South Uist Benbecula Muir of Ard An Radio 78550 854100 12 12 100 Dir 8A 195.936 SS_Scot_1969 SC19_CR254L South Uist North Uist Loch Portain An Radio 94950 872800 41 12 100 Omni 8A 195.936 SS_Scot_1970 SC19_CR254A South Uist South Uist Askernish An Radio 75750 823500 111 15 100 Dir 8A 195.936 SS_Scot_19


54


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1 NI2_CR139 Belfast Lisburn LisburnLisburn City Radio 138500 520600 42 30 100 Omni 9A 202.928 SS_NI_2

2 NI2_CR045 Belfast Lisburn BFBS Lisburn BFBS Lisburn 137938 522052 70 58 100 Omni 9A 202.928 SS_NI_23 NI2_AL295 Belfast Belfast Black Mountain U105 140112 528693 287 190 100 Dir 9A 202.928 SS_NI_2

6 NI2_CR129 BelfastAldergrove & Antrim RAF Aldergrove

Aldergrove & Antrim FM 128392 536663 83 21 100 Omni 9A 202.928 SS_NI_2

7 NI2_CR127 Belfast Bangor Conlig Bangor FM 162200 531900 101 16 100 Omni 9A 202.928 SS_NI_28 NI2_AL042N Belfast Newtownabbey Carnmoney Hill City Beat 146763 538362 202 50 100 Omni 9A 202.928 SS_NI_210 NI2_CR062 Belfast Belfast Europa Hotel Belfast FM 144067 529405 10 49 100 Omni 9A 202.928 SS_NI_212 NI1_CR060G Larne Larne Glenarm Chaine FM 146141 572045 93 10 100 Dir 8A 195.936 SS_NI_113 NI1_CR060B Larne Larne Balleygalley Chaine FM 153142 562408 67 9 100 Dir 8A 195.936 SS_NI_114 NI1_CR060L Larne Larne Balleylumford Chaine FM 156848 556469 0 53 100 Dir 8A 195.936 SS_NI_116 NI3_CR047 Downpatrick Downpatrick Downpatrick Down FM 159600 498320 60 20 100 Omni 7D 194.064 SS_NI_318 NI4_CR046 Kilkeel & Newry Newry Newry Golf Club IUR 115900 481700 159 12 100 Omni 8A 195.936 SS_NI_419 NI4_AL316K Kilkeel & Newry Kilkeel Kilkeel Q100.5 135759 474153 0 33 100 Dir 8A 195.936 SS_NI_4

21 NI5_CR048Portadown & Banbridge Banbridge Scarva Street Shine FM 121277 503297 97 15 100 Omni 8B 197.648 SS_NI_5

22 NI5_CR059XPortadown & Banbridge Portadown Portadown Bridge FM 114259 512832 59 15 100 Omni 8B 197.648 SS_NI_5

24 NI6_AL275 Cookstown Cookstown Tulnagee Quarry Mid Ulster FM 96064 547273 272 12 100 Dir 9C 206.352 SS_NI_625 NI7_AL301 Ballymena Ballymena Portglenone Q107 115775 561000 189 18 100 Dir 7D 194.064 SS_NI_7

26 NI8_AL254Ballymoney & Coleraine Coleraine

Maddybenny More Q97.2 102711 597071 63 51 100 Dir 9B 204.64 SS_NI_8

27 NI8_CR061Ballymoney & Coleraine Ballymoney Ballymoney fUSe FM 111740 584142 37 43 100 Omni 9B 204.64 SS_NI_8

29 NI9_AL155 Londonderry Londonderry Minkey Hill Q 102.9 FM 56100 580601 197 25 100 Dir 9A 202.928 SS_NI_9

31 NI10_AL270Omagh & Enniskillen

Omagh & Enniskillen

Brougher Mountain II Q101.2 FM West 46100 516848 269 39 100 Omni 9A 202.928 SS_NI_10

32 NI11_AL275 Dungannan Dungannan Dungannan Q106/7 91400 522700 111 20 100 Dir 8A 195.936 SS_NI_111 WA32_CR999 Chepstow Chepstow Chepstow Chepstow 354800 195600 69 15 100 Dir 9B 204.64 SS_Wales_322 WA27_CR122 Cardiff Barry Barry BRO Radio 311900 169700 60 20 100 Dir 9C 206.352 SS_Wales_273 WA27_CR094 Cardiff Cardiff Butetown Radio Cardiff 318700 175200 4 48 100 Dir 9C 206.352 SS_Wales_27

5 WA28_CR004 Pontypridd Pontypridd Bryn Tail Farm GTFM Pontypridd 309309 189876 252 15 100 Dir 9B 204.64 SS_Wales_286 WA29_AL257 Bridgend Bridgend Mynydd Baedan Bridge FM 287211 185476 242 30 100 Dir 8B 197.648 SS_Wales_29

7 WA30_AL306 Swansea South Swansea South Kilvey HillSwansea Bay Radio 267200 194050 189 20 100 Dir 7D 194.064 SS_Wales_30

8 WA31_CR111 Swansea North Swansea North Tircoed Radio Tircoed 262000 200100 67 18 100 Dir 9C 206.352 SS_Wales_31


55

Notes on site data table

ICS Telecom Call sign

Each transmitter site in the plan has a unique reference, used as the ICS Telecom ‘Call Sign’.

e.g. SW2_CR114

CR: Community Radio

AL: Small Scale/Low Power FM Radio

The Licence Number (taken from the Ofcom technical licensing database) has been shortened by not including the leading digits (generally 000 or 100). Where several transmitter sites form a service, an additional letter has been added to differentiate between sites. Because the leading digits have been dropped, the ‘call sign’ can only be indicative.

Code Region Planning Area

SW South West South West

S South South

LNE London: North East South

LNW London: North West South

LSE London: South East South

LSW London: South West South

LCE London: Central South

E East East

M Midlands

NW North West, Manchester & North Wales North West

N North North

NE North East North East

SC Scotland Scotland

WA Wales South West

NI Northern Ireland Northern Ireland

Table A3.1 Planning Areas Codes

Station in group/multiplex 2 of South West planning area, with the Community Radio Licence CR000114.

Small Scale DAB Feasibility Study – UK & NI

56

ICS Stn

If the stations within a region were loaded into ICS Telecom, this would be the transmitter number.

ICS Telecom EWF Files

ICS Telecom File Planning Area

SS_SW_V1.EWF South West

SS_W_V1.EWF Wales (South Wales)

SS_S_V1.EWF South (Including London)

SS_E_V1.EWF East

SS_M_V1.EWF Midlands

SS_NW_V1.EWF North West (Including Manchester)

SS_N_V1.EWF North

SS_NE_V1.EWF North East

SS_SC_V1.EWF Scotland

SS_NI_V1.EWF Northern Ireland

Table A3.2 ICS Telecom Planning Area Files

Within the ICS Telecom (.EWF) files, sites are listed that are not used. The best combination of sites, used to provide existing services, have been selected to provide the composite DAB service. The ‘User/Infra’ category has been assigned ‘1’, if the site is actually used.

Where several sites operate together to form a group, in ICS Telecom a nominal site has been created to model the combined coverage. The call sign of this nominal site includes the characters ‘COMP’.

e.g. SW2_COMP

Single sites or a composite nominal site forming a multiplex area have the ICS Telecom ‘Link’ category assigned as ‘1’.

Sites list or multiplex areas list can be created within ICS Telecom (.EWF files) by filtering on the ‘User/Infra’ and ‘Link’ categories.

Network ID

Each multiplex area in the plan has a unique reference, used as the ICS Telecom ‘Network ID’.

e.g. SS_Southwest_2 Station Group/Multiplex 2 in the South West area.


57

Annex 3

3 PMR Protection Calculations Maximum DAB Field Strength at PMR Receive Antenna

Assuming:

• Noise floor of the PMR receiving system, referred to the receiver input is -111dBm within a 12.5 kHz bandwidth.

• Receive antenna gain 0dBd • Feeder Loss 4dB

We do not want to increase the noise floor by more than 1dB.

Consequently, the DAB power at the receiver input within a 12.5 kHz bandwidth should be 6dB less (10 Log (1 + ¼) = 0.97)

So maximum DAB power at receiver input should be -111dBm – 6dB = -117dBm

Referred to the receive antenna this would be -117dBm + 4dB = -113dBm

For a 50Ω system, this would be a voltage of -6dBµV at receive antenna output.

The receive antenna is assumed to have no gain relative to a dipole, so the antenna factor (terminated dipole) is 20*Log �2𝜋𝜋𝜆𝜆 �, where λ = f/300 (frequency f in MHz)

At 200MHz the antenna factor (terminated dipole) is approximately 12.4dB

Maximum allowed DAB field strength in 12.5 kHz bandwidth would be -6dBµV + 12.4dB/m = 6.4dBµV/m.

Within the 1536 kHz DAB bandwidth, this would be 6.4µV/m + 10*Log�153612.5 �dB = 27.3dBµV/m.

Rounded:

Maximum (effective) 14 DAB Field Strength at PMR Receive Antenna = 27dBµV/m

14 For base station reception, the directional receive antenna discrimination is also taken into account.

Small Scale DAB Feasibility Study – UK & NI

58

PMR Base Station Parameters

Operator Site NGR TX in Blocks

Rx in Blocks ERP Ae Height Pattern

Zycomm High Bradfield SK278933 9A, 9B

7D, 8A, 8B 15W 30m Dir 20º

Zycomm Alport Height SK306516 9A, 9B

7D, 8A, 8B 25W 30m Dir 100º

Zycomm Zycomm Radio Site SK346199 9A, 9B

7D, 8A, 8B 25W 35m Dir 135º

Merseyside Transport

Hatton Green

SJ345909 9B, 9C 8B 25W 27m Dir 110º

Small scale DAB trials Annex 2: Technical background and architecture

Research Document


Small scale DAB trials Annex 2: technical background and architecture

About this document This document accompanies Ofcom’s final report on the small scale DAB trials. It provides a more in-depth technical account of the development of a ‘production ready’ DAB platform based upon common, off-the-shelf computer hardware running Free and Open Source Software.

This document is primarily aimed at a technical readership, and assumes familiarity with the DAB technical standards and radio engineering techniques


Contents

Section Page 1 Introduction 1

2 Encoding 2

3 Ensemble multiplexing 6

4 Modulation 9

5 Amplification 10

6 Filtering 11

7 Contribution and distribution 13

8 Aerials and feeders 14

9 Commissioning 16

10 Coverage and adjacent channel interference 17

11 Lessons: Single transmitter trials 20

12 Lessons: Single Frequency Network trials 22

13 Lessons: On-channel repeater trial 24


1

Section 1

1 Introduction 1.1 The small scale DAB trials are based upon low cost hardware and open source

software. In this document we describe the components of the small scale DAB transmitter systems used in the trials, and some technical lessons we have learned during the course of the three separate types of trial.

1.2 The main functional components of a typical system are audio encoding, multiplexing, modulation, power amplification, filtering, and a transmitting aerial, and these are illustrated in the diagram below.

Figure A1: Typical small scale DAB system block diagram


2

Section 2

2 Encoding DAB encoder

2.1 The initial Brighton small scale DAB trial of 2012/3 used the open source toolame 02l Layer II audio codec, which had been unmaintained since 2003.

2.2 Open Digital Radio (www.opendigitalradio.org, ODR) is a not-for-profit organisation based in Switzerland whose purpose is to develop software tools which aim to make it easier to access digital radio broadcasting technology. ODR adopted the abandoned toolame source code and developed a new ‘fork’ (independent development) of the software in order to adapt it further with the aim of making it more ‘user friendly’ for broadcasting use.

2.3 The toolame application supports all valid sampling and bitrates and comes with a selection of tuned psychoacoustic models in addition to the original ISO MPEG working group Dist101 reference implementation. These additional models enable further optimisation of quality to suit different output rates. The sonic differences between the models are notable, so it is critical to select the appropriate model to optimise the sound quality. Mono, joint and full stereo modes are all supported.

2.4 The ODR fork of this code (named toolame-dab) has been enhanced with the addition of a flexible input library (libvlc) which provides the ‘glue’ between the application and many different kinds of audio sources. There is also an input for text and images to be transmitted inside the frames as Programme Associated Data.

2.5 Outputs can be saved to a file, or sent to multiple remote destinations via IP. When the encoder application is sending data to the multiplexer, a distributed transaction protocol called zeromq is used. One useful feature of zeromq is that it supports a layer of elliptic-curve cryptography which provides optional authentication and security. Encryption keys are generated on the multiplexer; these are then loaded on to the authorised encoders manually before they are deployed.

2.6 The audio encoding units supplied to small scale DAB trial operators supported MPEG-1 Layer 2 audio only, but could also deliver DAB+ bitstreams by loading an additional software application. An important design consideration of the trial systems was that they should be of the lowest technical complexity possible, as it was assumed that mostly inexperienced operators would be using the system.

Multimedia Object encoder

2.7 Both the DAB and DAB+ encoders support the transmission of Programme Associated Data via a Multimedia Object Transfer helper application developed by Italian research organisation CSP2. This is used in conjunction with the encoder application, which together enable an X-PAD (EN 301 2343) transmission of Dynamic Label Segment (DLS) text data and/or multimedia objects such as images.

1 Downloadable from ftp://ftp.tnt.uni-hannover.de/pub/MPEG/audio/mpeg2/software/technical_report/dist10.tar.gz 2 www.csp.it 3 http://www.etsi.org/deliver/etsi_en/301200_301299/301234/02.01.01_60/en_301234v020101p.pdf

http://www.opendigitalradio.org/

ftp://ftp.tnt.uni-hannover.de/pub/MPEG/audio/mpeg2/software/technical_report/dist10.tar.gz

ftp://ftp.tnt.uni-hannover.de/pub/MPEG/audio/mpeg2/software/technical_report/dist10.tar.gz

http://www.csp.it/

http://www.etsi.org/deliver/etsi_en/301200_301299/301234/02.01.01_60/en_301234v020101p.pdf


3

2.8 During the development phase of the project, Ofcom selected and built replicable systems for both ARM and x86/64 platforms. A micro SD card image was prepared for the Beaglebone, Raspberry Pi, and Odroid C1, U3 and XU4 single board computers. The Odroid U3 and Odroid C1 were initially selected for deployment during the main trials, and over sixty units were prepared on the assumption that each trial might carry up to six services unique to that particular multiplex. Trial operators were encouraged to provide additional encoders as required, and invited to use the units provided as a template.

2.9 The encoder parameters and destination IP address are configured by connecting a display and keyboard to the encoder or by using a secure terminal program. The operating parameters are contained in a simple script which can be edited manually to make changes. The script also places the encoder in a controlled loop to enable automatic recovery in the event of accidental disconnection or replacement of the sound input device.

2.10 During the course of the trials, an ODR user in France released a helper application based on ‘Supervisord’ called ‘ODR Encoder Manager’4. This enables the setting of all parameters, and the addition of multimedia objects, via devices on the same network segment using a web interface. The ODR Encoder Manager has an API, and the Dynamic Label Segment text and multimedia (slideshow) content can be updated automatically from the studio playout and automation software. The encoder manager was developed after the encoder design for the trial was frozen for release. Therefore, the trial units did not contain the web configuration option.

Encoder hardware

2.11 ‘Smart device’ development has led to the availability of small form factor, low-cost yet relatively powerful single board computers. Most of these development platforms use ARM processing cores optimised for battery powered use, so they use very little electricity when compared to a typical home or office desktop PC. These ARM cores had already been used by Ofcom engineers to form building blocks of the DAB platform, and their potential had been established. The Raspberry Pi computer was initially used as our main encoder development platform, but this was later superseded by the Odroid U3 and the Odroid C1 because of some storage media compatibility issues experienced with the Pi.

2.12 It was planned that up to six source encoders would be provided to each of the ten triallists. It would not have been practical for us to provide audio encoders based on desktop PCs or low-powered 1RU servers due to storage and working space constraints. It was therefore decided that only ARM single board computers would be used for encoding. A quantity of Odroid U3 and Odroid C1 units were procured, and fitted with suitable SD cards or eMMC modules which we had prepared by copying the operating system and the DAB encoding applications on to them.

2.13 It was later found that one of the models of single board computer would freeze unpredictably. This problem was eventually traced to a combination of a power supply smoothing issue on the board, along with poor quality USB On-The-Go (OTG) cables which exhibited a high series resistance (and which resulted in a significant voltage drop on the USB 5 volt rail). The USB OTG cables had been procured as they were needed for the sound input devices due to a different, but well understood, limitation with the full size USB ports on the single board computer. We observed a pattern whereby certain encoder installations experienced seemingly random

4 https://github.com/YoannQueret/ODR-EncoderManager

https://github.com/YoannQueret/ODR-EncoderManager


4

failures, while others had this type of encoder in operation with no such behaviour being experienced. The alternative single board computer units were no longer in production so the Odroid XU4 (a newer, more powerful unit) was offered as a replacement for any troublesome units. The replacements have subsequently proven to be very reliable in service.

2.14 The lessons learned from this experience are that single board computers consume little power, and with careful hardware and peripheral selection they can be used as a reliable, low cost encoding solution that takes up very little physical space. Using desktop or industrialised computers could be an alternative approach given their more predictable performance, their robust construction, and their wide availability and interchangeability.

Input audio signal conditioning

2.15 Radio broadcasters use dedicated audio processing units to control dynamic range and to create a ‘signature sound’ for their stations. These units prevent undesirable overload distortion and can also correct low audio levels. A small number of audio levelling units were procured and distributed to triallists in case they encountered problems with audio level control, or maintaining level consistency between different services in the ensemble. These units do not employ aggressive multiband compression and it was found that as well as providing consistency to the programme levels, there was a noticeable reduction in audible encoding artefacts. If a more powerful PC architecture were to be used for encoding, it may be practical to integrate audio level control within the encoder as another software application.

Sound interface devices

2.16 Many different sound devices are supported in the Linux kernel, so the primary consideration was to balance cost and quality. A £25 semi-professional unit was selected which provides good analogue audio performance (equivalent to some units costing several times more). Many small stations have studios which mix audio in the analogue domain, and this was the interface of choice for the majority of services carried on the trials. Using analogue audio avoided potential problems caused by clocking and sample rate mismatches which can sometimes occur when interfacing different equipment in the digital domain. An S/PDIF digital audio interface was also tested and was used by some services. This interface also accepted AES3 (AES/EBU) bitstreams, when carefully unbalanced and level adjusted. The digital sound device was roughly the same cost as the analogue device and it provided a clearly audible improvement in audio quality – especially when fed from an entirely digital programme chain.

DAB+

2.17 DAB+ employs the HE-AAC audio codec which requires approximately half of the data rate for similar subjective performance to an appropriately optimised MPEG-1 Layer 2 codec. The codec offers a greater choice of sampling rates, and other extensions which can be used to enhance subjective quality when used for bandwidth sensitive applications like broadcasting and streaming. One such technique is called Spectral Band Replication. SBR is used by halving the AAC sampling frequency, and replacing the high frequencies with instructions which enable the decoder within the receiver to artificially reconstruct the high frequency sounds.


5

2.18 An additional technique which further reduces the overhead is parametric (or synthetic) stereo which provides additional rate savings beyond what can be achieved with the common ‘joint stereo’ modes in other codecs. This involves running the AAC core in mono. Parametric Stereo uses similar techniques to SBR to send positional information which the decoder can use to reconstruct the stereo image.

2.19 HE-AAC also employs an additional layer of Reed-Solomon error correction which can help to improve reception, which is a particularly useful property for small scale multiplexes. Subjective listening tests indicate that HE-AAC can deliver good quality stereo audio at around 80 kb/s. It is also capable of delivering lower fidelity stereo at lower rates than Layer 2 through the use of parametric stereo and Spectral Band Replication.

2.20 The first regular use of DAB+ in the UK was introduced by Solent Wireless, who operate the Trial Portsmouth multiplex. Their technical partners, Commtronix Limited, became holders of a unified AAC licence through VIA Corporation (the company which operates a patent pool on behalf of the intellectual property rights holders for AAC). The technical partners subsequently supplied encoders to services on other trial multiplexes who wished to broadcast using DAB+.

2.21 Because the DAB+ codec provides acceptable sound quality at lower bitrates than the DAB codec, it has been used to relieve ‘congestion’ on some trial multiplexes. Because carriage costs for DAB services are generally proportional to the capacity resource occupied on a multiplex, a DAB+ service is usually cheaper to transmit than a DAB service. Therefore, we expect that services may adopt DAB+ where minimising carriage costs is a priority, or where a presence on the broadcast platform is more important than ubiquitous reception (while almost all DAB car systems can receive DAB+, this is not yet the case with domestic sets).

2.22 The concept of small scale DAB relies on the use of relatively low power transmitters for several reasons. These include maximising the re-use opportunity of scarce frequency resources, minimising the risk of receiver blocking (ACI), and keeping the capital and operating costs at modest levels. While these place constraints on the transmitter power levels that might be used for small scale, the newer DAB+ codec can help to improve reception quality and reliability while at the same time avoiding an increase in outgoing interference. This is because DAB+ has a lower signal-to-noise requirement than services encoded with the Layer 2 codec.

2.23 Most DAB+ capable receivers contain the most recent generation of silicon receiver technology. These integrated circuits and modules generally provide much better sensitivity than their predecessors. These receivers can provide a markedly better end-user experience as a result. The digital tick mark5 helps consumers to select a radio which can receive new DAB+ services and which achieves a minimum level of sensitivity.

5 http://www.getdigitalradio.com/industry/what-is-the-tick-mark/

http://www.getdigitalradio.com/industry/what-is-the-tick-mark/


6

Section 3

3 Ensemble multiplexing Overview

3.1 The multiplexer is the heart of any DAB transmission platform. It accepts data from multiple sources (local and remote streams or files) and combines them into an output known as the Ensemble Transport Interface (ETI). This is the standardised format accepted by first-generation commercial DAB modulators. The ETI stream was originally presented on the G.703/4 interface once common in carrier grade telecommunications equipment. DAB multiplexers and transmitting plant included the interface as it was the logical technology to use at the time when DAB was developed. This interface has since been replaced with a more modern approach of ETI encapsulated in IP packets which enables use of the now ubiquitous Ethernet interface – this is known as the Ensemble Distribution Interface (EDI). Multiplexers can accept a mixed payload of audio encoded in either of the standardised DAB or DAB+ formats, as well as other data and signalling for advanced features and other applications.

3.2 The original 2012/2013 Brighton test used crc-dabmux, an ensemble multiplexer which was created by the federally-funded Communications Research Centre of Canada6. CRC opened the source of the suite under the General Public Licence shortly before ceasing development entirely. The code was subsequently adopted and is being further developed by Open Digital Radio, which has a collective of users and contributors in a number of countries.

3.3 The evolution of crc-dabmux into ODR-DabMux has seen the application evolve from a lab demonstration tool into a ‘production ready’ DAB head-end which is now in full time use in a number of countries. It accepts text files for configuration, uses robust zeromq streams for both input and outputs, handles time-stamping for SFN functionality, and supports a number of implemented information groups which provide additional signalling for applications such as traffic announcements. The application release is v1.1 at the time of writing. The version numbering reflects that the application has now reached a milestone in functionality and stability.

3.4 During the course of the UK small scale DAB trials, the software (when correctly configured) has proved to be robust even in challenging network conditions. Almost all programme feeds in the trials are delivered across public Internet connections, yet provided acceptable performance even in the absence of a standby connection. Higher resilience could be easily achieved by duplicating the encoders, or more simply with a failover or active redundant connection. Fixed Wireless Access operating in the 5 GHz WiFi band has also been used, and appeared to work well for providing connectivity to some multiplexers. One exception was where a 5 GHz link end-point was located close to an establishment which tests marine radar systems in the same spectrum segment.

3.5 Although the multiplexer application itself is ‘lean’, and contains no integrated monitoring functionality, it offers interfaces to common statistical analysis tools, such as Munin graphs, which enables comprehensive monitoring and fault reporting. The

6 http://www.crc.gc.ca/eic/site/069.nsf/eng/home

http://www.crc.gc.ca/eic/site/069.nsf/eng/home


7

addition of the Ensemble Distribution Interface provides interoperability with the latest generation of commercial DAB modulators.

3.6 The ODR-DabMux application is compliant with ETSI standard EN 300 4017 but not all features in the specification have been implemented at this time. Nonetheless, it has proven to be more than adequate for broadcasters who wish to gain a foothold on the digital radio platform with minimal outlay, and for those wanting a basic yet functional solution that requires little maintenance or user intervention.

3.7 The primary current limitation of ODR-DabMux is that only certain parameters like service labels can be changed dynamically. Major configuration changes (such as the removal or addition of a service) require the multiplexer application to be restarted. This causes a momentary disruption to all services carried in the ensemble. It is therefore good practice to only apply such changes during planned maintenance windows.

3.8 The original crc-dabmux application only accepted configuration through complex command line arguments issued at run time or via a script. It has since been enhanced to support configuration files. This enables configuration templates to be prepared and checked for correctness on a separate staging system before being placed into the production environment. The configuration file contains the global ensemble parameters (EId, SIds, labels, transmission mode flag, SFN time-stamping) as well as the service parameters and output formats.

Issues

3.9 The ODR-DabMux multiplexer has proven to be reliable and dependable, but some industry stakeholders who carried out their own analysis of the multiplex structure expressed some concerns. The first issue related to the toggling of the time confidence indicator, which was an intentional feature introduced as a means of identifying where the ODR software was in use (watermarking). This feature was deemed to be undesirable, and non-compliant with EN 300 401, and was quickly rectified.

3.10 The same stakeholder also suggested that the repetition rates of certain data groups were low when compared to other multiplexes, and that this was non-compliant. However, the ETSI specification only makes recommendations about the repetition rates and does not define hard limits. A large sample of common DAB receivers was tested before bringing the platform into use to help ensure that there would be no negative impact to existing receivers. This was a sensible precaution as receiver technology providers do not share information about how their devices work due to commercial confidentiality concerns. During the trial the Fast Information Channel (FIC) carousel code was replaced by the Open Digital Radio lead developer Matthias P Brandli. This resulted in repetition rates of the Fast Information groups being increased.

3.11 Another stakeholder expressed concern about identical labels being used for both service definition and components. While this was not thought to be an issue for receivers complying with the standards, the duplication was due to a problem with parsing configuration files present in the version of ODR-DabMux which was used for the trials. This was subsequently patched so the duplicate component label could be removed if the operator wished to do so.

7 http://www.etsi.org/deliver/etsi_en/300400_300499/300401/01.04.01_60/en_300401v010401p.pdf

http://www.etsi.org/deliver/etsi_en/300400_300499/300401/01.04.01_60/en_300401v010401p.pdf


8

3.12 The open source code is available to be scrutinised by any interested party. This enables both constructive feedback and code contributions for enhancements and fixes. The stakeholder observations and feedback that we received have been most useful in ensuring that the multiplexer is compliant with the relevant ETSI standards.

3.13 Since the trials were announced we have become aware that several companies have begun to tailor products specifically for smaller scale DAB applications. These include content severs, multiplexing software and ‘one box’ solutions.

Trial developments: Hardware

3.14 Following on from a previous experiment which demonstrated that a single core ARMv6 processor operating at 700 MHz could ‘just about’ run the multiplexer, it was clear that commodity System-on-Chip units could offer a compact, low-maintenance, low-cost and low-power solution. More powerful mini desktop computers could also provide a 'one box solution' for certain applications. The Odroid U3 development single board computer (SBC) was initially selected for the trials, and the multiplexer application was compiled on the Ubuntu GNU/Linux computer operating system. This proved to be a good combination.

3.15 The $65 Odroid U3 SBC was demonstrated to stakeholders, and endurance tests demonstrated that it was suitable for use in the trials. However, it was decided that an Intel Core i5 NUC PC would be used instead, as this solution afforded more flexibility in terms of tasks which could be consolidated into a single box, and it also provided more ‘headroom’ for future developments. Another consideration was that spares or replacement equipment would be much easier to obtain quickly if needed.

3.16 A potential alternative tested during the original test was to host the multiplexing application on a Virtual Private Server, or cloud. This provides the advantage of high bandwidth, good peering of networks, maintained power, environmental conditioning and fault tolerance. The disadvantages are not being in control of maintenance windows or having any direct relationship with intermediate networks. While cloud multiplexing worked well in testing it was considered risky for deployment during the trials because a fault or failure would affect all of the services in the ensemble.

3.17 A few services participating in the trial are however using encoders which run in the cloud. A cloud encoder typically connects to a high bitrate internet stream which is then transcoded to a DAB or DAB+ compatible format and sent onwards to the multiplexer. This is a quick and simple solution but should normally be avoided if possible, as passing the audio through different audio compression codecs can produce unpleasant audible artefacts.

3.18 The trial ensemble multiplexers were manufactured with a generic ‘template’ configuration consisting of six services at 192 kb/s stereo at UEP level 3. This equates to 840 capacity units out of the 864 available. Initially, changes to the configuration files needed to be carried out manually in a text editor, but some trial operators have added their own Graphical User Interface (in the form of a web interface) to make managing the multiplex possible by non-technical personnel.


9

Section 4

4 Modulation Modulator

4.1 The final software application in the transmission chain is ODR-DabMod. This is a modulator compliant to EN 300 401 which reads the ETI generated by ODR-DabMux, and outputs the digital domain representation of the RF COFDM signal as complex I/Q samples. The application is capable of producing an output signal with higher resolution than is described in the ETSI standard.

4.2 The application is flexible and has been tested with several different radio hardware platforms. Configuration is carried out in a similar way to the multiplexer in that it can read a file which contains the operating parameters. ODR-DabMod is able to decode timestamps inside the ETI, which is necessary if it is to be used in SFN mode. ODR-DabMod supports time-stamp decoding and transmitter offset delays for this purpose.

4.3 The application release is currently at version 0.6 and it is anticipated that it will reach the version 1.0 milestone once Transmitter Identification Information functionality has been completely implemented (TII is a method of identifying individual transmitters in an SFN group to specially-equipped receivers). However, the current version is suitable for production use in standalone transmitters, multi-frequency networks, or single frequency networks that contain two transmitters. This is because with only two different channel impulses, it is simple (in most cases) to determine which transmitter the impulses are from. The modulator has proven to be very reliable in service in several countries. One issue affecting SFN launch delay timing was identified during the UK trials which appears to have been rectified as a result of some refactoring of the source code.

4.4 ODR-DabMod supports a standard ETI input for use in direct conjunction with ODR-DabMux. For deployments where the multiplexer and modulator are in different physical locations the ETI stream is encapsulated in a ZeroMQ distributed computing protocol. This has proven to be reliable for receiving the ETI stream via the public internet.

4.5 A baseband filter is followed by an optional re-sampler and a universal hardware driver for a range of popular software defined radio peripherals. Several other radio hardware platforms have been validated to work with the modulator. These can be used with a UNIX standard output by using a Linux pipe to pass the complex 32-bit IQ samples (or the lower-resolution 8-bit signed samples as defined in ETSI EN 300 401) to the appropriate middleware.

4.6 The COFDM samples require a digital-to-analogue conversion, and the resulting signal needs to be converted to the transmission frequency. This process was carried out by a Universal Software Radio Peripheral which is capable of operating in spectrum between 70 MHz and 6 GHz. The USRP produced a low-level signal which then was used as the drive for a linear power amplifier.

4.7 The completed systems were subject to pre-commissioning tests defined in ETSI EN 301 489-11 and in the Ofcom Digital Technical Code. The tests were conducted in conjunction with the power amplifier feeding an external bandpass filter with a suitable response characteristic. The RF energy was then dissipated by a 50 ohm radio frequency dummy load which had a power handling capability of 1 kW.


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Section 5

5 Amplification Overview

5.1 The RF power amplifier of a DAB transmitter must be a purpose-designed unit certified to comply with (amongst other things) electromagnetic compatibility regulations and the UK Interface Requirements8. This limits the choice of unit to those offered by companies who manufacture and test products specifically for DAB transmission applications. Market testing of amplifiers in the 100-300W RMS output power range revealed a notably large variation of prices.

5.2 The amplifiers selected for the trials were units of sound design offering the lowest ‘price per watt’. These units are certified and carry the appropriate ‘CE’ marking which is required for products placed on the market within Europe.

5.3 Two units from different manufacturers were selected for the trials in order to avoid potential batch problems, and to test that different amplifiers produced consistent performance. Both amplifiers are class AB linear designs and produce a fair amount of waste heat due to the low efficiency of the topology. This inefficiency is of little concern at the relatively low RF power levels required for the small scale concept. The two units selected were capable of 100 to 150 watts RMS power, and each unit cost less than £3,000 (excluding VAT).

5.4 Because the open source modulator solution does not support pre-correction at this time, it is not yet practical to use a more efficient amplifier topology. At higher power levels many amplifiers now employ the classical Doherty technique to improve efficiency.

5.5 Some faults were experienced with both amplifier types: two units had a reliability issue with the front panel metering, while the others contained RF power devices which were later identified to be from a bad batch. These problems were identified during functional and soak testing. Both suppliers were able to resolve the issues quickly.

5.6 All of the trials operate single-ended transmission systems. These have no built-in fault tolerance as there is only one unit of each element in the chain, and this includes the amplifier. All of the systems were supported from a central set of spares held at the Ofcom Radio Station at Baldock in Hertfordshire. When amplifiers failed during the trial they were promptly replaced with a spare. The suspected defective units were then repaired or replaced by the manufacturer.

5.7 The RF power amplifiers have been operating reliably since the initial teething problems. The considerable ‘burn-in’ that has elapsed since suggests that they should continue to operate reliably during the trial extension.

8 http://stakeholders.ofcom.org.uk/spectrum/technical/interface-requirements/

http://stakeholders.ofcom.org.uk/spectrum/technical/interface-requirements/


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Section 6

6 Filtering Overview

6.1 Bandpass filters are used to shape the spectral output of DAB transmitters in order to meet the stringent emission masks which protect services in the adjacent spectrum. These filters are relatively large and mechanically complex devices.

6.2 ITU-R BS.1660 defines three separate masks for different use cases, but only the critical mask is currently approved for use in the UK. The BS.1660 critical mask is intended to protect services in adjacent bands. Other countries may require the use of the BS.1660 super-critical mask for special cases where block 12D is used in specific areas, and the non-critical mask may to be used in other cases.

6.3 We considered whether mask filters might be necessary at all for very low power small scale applications, particularly if the modulator could adaptively monitor and compensate for non-linearity and unwanted spurious products. We quickly concluded that this was not currently practical for most use cases, and that filters would be required for the trial transmitters.

6.4 In some cases, backing-off amplifier power can result in a less stringent or complex filtering requirement. However, linear amplifiers deliver their maximum efficiency when they are operated as close to their maximum power output rating as possible. This is due to the standing current needed for the semiconductors to operate in their linear region.

6.5 Some suitable models of bandpass filter are now less costly than they once were, and fitting them habitually is good engineering practice – particularly if the station is installed in close proximity to other radio transmitters.

6.6 A filter rated at 250 watts RMS now costs around £1,000 which is not excessive considering the expected lifespan of the transmitter plant. It is also a safeguard against spurious emissions, and most transmitters (including commercial ones) would not be able to meet the ETSI specifications detailed in EN 301 489-11 without an external filter. Conformity is often achieved by describing the response characteristic of a (required) external filter.

6.7 The filters used in the trial were a frequency-agile component which needed to be ordered pre-tuned to the appropriate transmission frequencies for their eventual deployment. Market testing identified several potential suppliers, but only one offered a tuneable filter in the short lead-time needed. As frequency planning could not be carried out before sites were known, a few filters needed to be re-tuned prior to issue to triallists. The process requires a real-time Vector Network Analyser so this was carried out by an external contractor. The need to re-tune some filters showed that it is advantageous to use a frequency agile filter. However, this may be less of an issue where transmission frequencies are known and are essentially fixed from the outset of a deployment (e.g. in any future wider roll-out of small scale DAB).

6.8 Ofcom may explore the potential for the use of the non-critical mask (or some other form of mask relaxation) for low-power applications which may enable less complex filters and/or circulators to be used.


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6.9 It is still feasible that very low-power DAB transmitters could be made to comply with the emission requirements without using mask filters. This could be useful for other applications that might eventually use the technology. These could include MFN and SFN gap filling transmitters, or as a potential digital equivalent of long term Restricted Service Licences (LT-RSLs). These latter services currently use powers below 1 watt in the Medium Frequency band (or 50 milliwatts in the case of FM in certain areas) to serve specific establishments. These include university campuses, hospitals and schools. These potential applications have not been considered in detail as they are outside the scope of this project


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Section 7

7 Contribution and distribution Overview

7.1 Several different types of IP broadband circuits were used by the trials for the connectivity between encoders and ensemble multiplexers, and between multiplexers and distant transmitter sites (when needed to form an SFN). The circuits needed to provide sufficient aggregate throughput to transport the encapsulated ETI feed without interruption. This can be achieved by tuning buffers to store enough data to overcome the longest period of network stalling or contention observed during the testing phase.

7.2 Broadband contention ratios need to be low in order to prevent network loading by other users from causing interruptions. During the trials, low-cost business grade DSL circuits (without data transfer caps) were found to provide adequate performance for the stream ingress from multiple encoder sources. However, these circuits were not suitable for delivering the multiplexed ETI feeds to remotely located transmitters due to the inherent asymmetry between upload and download transfer rates.

7.3 For SFN operation in particular, circuits must offer predictable throughput with low error rates. Low cost 5.8 GHz Ethernet bridges and Ethernet over Fibre To The Cabinet (EoFTTC) have both been tested successfully for supporting SFNs.

7.4 A backup wireless bridge sustained a two-transmitter SFN during a prolonged circuit outage. The fault was severe enough for it to persist for six days beyond the contractual service level agreement which illustrates the importance of providing diverse connectivity paths to the ensemble multiplexer – a mix of bearer technology and service providers may reduce the risk of core and access network faults which may affect all connectivity paths provided by a single supplier.

7.5 For SFN applications in particular, EoFTTC and Ethernet First Mile (EFM) are currently available for point-to-point and any-to-any connectivity in around 90% of exchange areas. These products offer suitable performance, resilience, and a six-hour fault resolution in most circumstances. Such circuits should take around 25 working days from order to provision, but it was found in some cases that this took considerably longer in practice. The cost of EFM and EoFTTC is several times higher than the more common ADSL and VDSL services.

7.6 For non-SFN operation, the multiplexer may be co-located with the transmitter and the programme feeds can be delivered via any means considered practical, although off-air feeding should be considered the last resort due to the loss of quality and because of security concerns.


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Section 8

8 Aerials and feeders 8.1 Aerials are generally ordered for the frequency of interest and cut to length during the

manufacturing process. During procurement we identified a company that could deliver within the short lead time we needed in order to keep to our very tight launch schedule. The cost was also competitive so these were ordered as soon as the final site details and frequencies for the trials were known.

8.2 As we had neither sufficient time or resources to design a bespoke system for each trial it was decided to standardise on an end-fed co-linear aerial type with 3dBd of gain, as these were small enough to easily transport and erect. The gain made up for the system losses incurred in the mask filter and the feeder cable. The angle of radiation in the vertical plane was also beneficial for minimising blocking (ACI) providing the aerial was mounted at a reasonable height above the surrounding terrain and dwellings.

8.3 6dBd co-linear aerials were delivered to the London trial with the agreement of the operator due to heightened ACI concerns as both sites were in very densely populated areas, and because of the high number of existing multiplex services in the area. This aerial type was also helpful in ameliorating (to some degree) blocking caused by a business radio system with many mobile stations, and ‘reverse ACI’ from other DAB networks which lay down much higher field strengths (due to the greater number, and higher power levels, of the transmitters in those networks.)

8.4 At a few sites, triallists proposed to use existing mast structures rather than rooftop sites. Existing mast sites were provided with cardioid pattern aerials to largely de-couple the effects of the supporting structure on gain and pattern. A cardioid aerial was also provided for the on-channel repeater site. These aerials were later replaced as they were found not to provide the claimed high front-to-back ratio, or the horizontal radiation pattern expected.

8.5 The feeder cable selected for the trials was of a coaxial type with a rated loss of circa 6dB per 100m at 200 MHz. The seven-strand inner conductor, polyurethane dielectric, and copper braid screen made it more attractive than the lower loss solid conductor cables with a PVC coated corrugated copper screen as the latter are more susceptible to damage from crushing and bending. The higher loss of the cheaper, more durable cable was therefore considered to be acceptable.

8.6 One operator installed their own cable instead of the one supplied. This was discovered on commissioning due the connectors being a noticeably poor fit. The cable used, RG214, has a considerably higher loss of ~11dB/100m at the frequencies of interest. The cable braid also caused a short circuit at the output of the mask filter as the connectors were not the correct parts for the cable used. No damage was caused, but the system losses were much higher, particularly as the cable run was quite long.

8.7 Another operator installed a gas discharge lightning arrestor in the feeder cable at the request of the site landlord. The site failed commissioning due to poor spectral purity, and the arrestor was eventually found to be the cause of the problem. It is thought that the high crest factor of the DAB signal was causing electrical breakdown in the arrestor due to the peak voltages approaching or exceeding the striking voltage.


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8.8 Two trial transmitters were installed in buildings also containing communal aerial distribution amplifiers. The DAB transmitters were found to cause problems to domestic digital terrestrial television (DTT) reception. Many domestic aerial amplifiers have a very wideband response, and operate at VHF frequencies in addition to the UHF band used for TV. The proximity of the DAB transmitting aerials caused these amplifiers to be overloaded.

8.9 The commissioning process was suspended while bandpass channel filters were fitted to the input of each aerial distribution amplifier. This resolved the problem in both cases. Interference to domestic reception did not occur at other trial transmitter sites.


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Section 9

9 Commissioning 9.1 The small scale trial multiplexes were subjected to the same commissioning checks

which are carried out for all DAB transmitters in the UK. These included pre-compliance checks by the operator of the service for and health and safety issues, including prevention of public exposure to excessive levels of non-ionising radiation. Once installed and fully prepared by the trial operator, Ofcom engineers then carried out drive surveys of existing DAB multiplex signal levels in the vicinity of the transmitter. We then visited the transmitter site to carry out a full commissioning of the system into antenna, and carried out a further coverage survey of existing DAB multiplexes to ensure that their coverage was not impacted by ACI caused by the trial transmitter.

9.2 The on-site commissioning process consists of measuring the operating frequency, power and spectral occupancy (including spurious and harmonic emissions) to ensure they are within the tolerances set out in Ofcom’s Digital Technical Code9. We also check the aerial installation for compliance with the Code and that the agreed mounting position has been used.

9.3 As the trial multiplexes began to launch, Ofcom formed three different commissioning teams to spread the workload. Whilst most services were commissioned without any issues there we a few instances where remedial work was needed before the transmitting station could be brought into service. One notable instance where further work was required was where building work had commenced shortly after installation of the antenna system. The builders erected scaffolding in very close proximity to the transmitting antenna, resulting in a possible infringement of the ICNIRP regulations and presenting a possible RF safety hazard to building workers. Transmissions were ceased until the aerial could be repositioned and re-tested.

9 http://stakeholders.ofcom.org.uk/binaries/broadcast/guidance/tech-guidance/digi_tech_code.pdf

http://stakeholders.ofcom.org.uk/binaries/broadcast/guidance/tech-guidance/digi_tech_code.pdf


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Section 10

10 Coverage and adjacent channel interference Coverage

10.1 We set the trial operators a challenging, but achievable, timeframe to launch of twelve weeks from the offer of a trial licence. This was necessary to ensure the multiplexes were broadcasting for a reasonable amount of time during the period in which project funding was available.

10.2 This, coupled with the temporary nature of the trial, was not conducive to operators securing the best transmission site in many cases. For example, it can often take considerable time to negotiate access and then secure agreements with site landlords. It was therefore expected that most operators would utilise sites for which they already had an agreement to use, or ones that could be quickly secured for the duration of the trial at minimal cost.

10.3 One operator informed us that they deliberately used a site that they owned, and that they were aware its coverage would be relatively poor. However, they considered that the technical aims of the trial could be met even when a sub-optimal site was used.

10.4 Another triallist moved to a better-suited site part of the way through the initial trial period. The opportunity to study this site move provided valuable insight into how operators might move a ‘live’ site. Other operators have subsequently submitted various proposals to change or add transmitter sites. These were considered on a case-by-case basis for their novelty, and if we could learn anything useful from the proposal, with a general constraint that a site move should not cause the coverage area of the multiplex to be extended beyond that which was originally achieved and/or applied for.

10.5 None of the operators chose to employ higher levels of error protection in order to optimise coverage. Presumably either this was because the coverage was satisfactory, or because of the cost to capacity resources. All services on the trials currently employ UEP3 for DAB or EEP-3A for DAB+. The latter generally appears to have been used to fit a greater number of services into the multiplex rather than for enhancing coverage or improving sound quality.

10.6 DAB+ at EEP-1A could reduce the signal-to-noise requirement by up to circa 4.5dB when compared with DAB at UEP3. This would provide a significant gain for multiplexes seeking to improve reception robustness or coverage, and (unlike a power increase) does not increase outgoing interference or the risk of ACI.

10.7 Receiver performance can also significantly affect the perception of coverage. We tested a sample of receivers and found a very significant variation in sensitivity. We later contracted the DTG to carry out independent tests. The DTG report (Annex 6) correlated closely with our findings. There was a circa 20dB difference in sensitivity between the best and worst receivers in our sample. Most newer sets which support DAB+ use the latest generation of receiver technology, and are also more likely to


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carry the ‘digital tick mark’ which requires sets to meet or exceed a minimum sensitivity level.

Adjacent Channel Interference (ACI)

10.8 When a licensee wishes to bring a new DAB transmitter site into operation Ofcom considers whether and to what extent this might lead to ‘hole punching’ in the coverage of other multiplexes on adjacent-channel frequencies which serve the same area.

10.9 When considering the impact of ACI for the small scale DAB multiplex trials, we adopted the same process as used for existing DAB multiplexes. The principles for the management of ACI are set out in the ‘Ofcom Technical policy guidance for DAB multiplex licensees’10 document.

10.10 Ofcom engaged with the relevant licensees once the transmission parameters for the trial sites were finalised and an initial prediction was run in order to gauge the likely levels of interference. Ofcom also met with the BBC and Arqiva spectrum planners to form an initial view of the shortlisted sites. These assessments were carried out in a manner consistent with that adopted by the JPRG11 ACI sub-group.

10.11 We expected that transmitters for these trials would operate with an ERP of around 100 watts and generally be on frequency block 9A or 9C, although some exceptions assumed operation on block 10B or 10D. The use of frequency blocks not currently occupied by DAB reduces the potential for ACI to occur. Our initial assessment was that some of the proposed SS DAB sites presented a very low risk of causing ACI, while others were thought to likely require some mitigation.

10.12 Given the limited trial duration, it was not proportionate to consider the implementation of filler transmitters. We therefore proposed to attend the commissioning of all of the trial SS DAB sites and measure the coverage of existing services within 500 metres of the installation prior to and after commissioning. This was necessary to gauge the magnitude of any interference or blocking.

10.13 We intended to mitigate any significant impact through measures such as modifying antenna arrangements and/or power reductions. Furthermore, all of the small scale DAB trial licences contained a provision through which we could require the transmissions to cease if they caused undue interference to other services.

10.14 In practice, the blocking effect caused by the trial transmitters was far less evident than was predicted by computer modelling, and at worst there was a small reduction of the percentage of locations served in the immediate vicinity of the site.

10.15 We believe the reason for this is because the prediction tool will produce a 'worst case' result because such tools do not have sufficient resolution in their models about the local environment - for example they lack information about buildings or vegetation, which can attenuate radio signals and therefore reduce the local signal levels below what would otherwise be a free space loss calculation.

10 http://stakeholders.ofcom.org.uk/binaries/broadcast/guidance/tech-guidance/policy_guidance.pdf 11 The Joint Planning for Radio Group: a group chaired by Ofcom which contains representatives of its digital radio multiplex licensees (and the BBC) which is used to develop Ofcom’s policies on digital radio spectrum management.

http://stakeholders.ofcom.org.uk/binaries/broadcast/guidance/tech-guidance/policy_guidance.pdf


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10.16 The protection ratios used to date for predicting ACI were established when lower resolution (8-bit) analogue to digital converters were used in receiver baseband processors. More recent receivers are thought to use higher resolution converters which enable them to process signals with a higher level variance, and so are less prone to blocking.

10.17 Generally, where the signal from other multiplexes was of a usable strength, no significant levels of blocking or ACI were detected, although one member of the public located approximately 100 metres from a trial transmitter reported the loss of reception of one multiplex. This problem was resolved when the listener repositioned the receiver.

10.18 At some trial sites, industry stakeholders carried out their own ACI measurement exercises in addition to the ones carried out by Ofcom. The findings by all parties were that there seemed to be very little correlation between audible errors and measured BER, with failures only noted where the signal strength of the trial transmitter was around 55dB above the wanted signal. While outside the scope of this project, this significant difference could provide an opportunity to re-assess the current methodology for predicting ACI, as these results indicate that a simpler approach could provide adequate protection for listeners. Remedies other than building filler transmitters also exist and could be considered.


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Section 11

11 Lessons: Single transmitter trials Overview

11.1 The single transmitter trial equipment was housed in a 12RU flight case for ease of integration and transportation. Although the active equipment only occupied 7RU, the larger case ensured there was adequate airflow, and an extra shelf provided a place for mounting the connectivity provider’s network termination and routing equipment.

11.2 The case contained a VLAN-aware managed network switch, a Core i5 NUC (a mini PC), B200 software defined radio and a VHF linear amplifier. A small line interactive UPS was also fitted to condition the mains supply for all components of the system apart from the amplifier. The UPS was also intended to provide isolation from the mains supply in case of commutation spikes and transients caused by nearby lightning strikes or other equipment which might be present on the same supply phase.

11.3 The NUC PC ran the Debian 8 GNU/Linux distribution which had been customised through configuration and the addition of the necessary software components. A set of configuration templates enabled the completed systems to be tested in a straight-forward and repeatable manner, and to enable them to be ready to operate into a radio frequency dummy load immediately after the final assembly had been completed.

11.4 In the standalone configuration, the ensemble multiplexer (ODR-DabMux) was configured to send the ETI stream directly to the modulator (ODR-DabMod) application using standard outputs and inputs. Linux pipes enable this data to be passed between the two applications directly.

11.5 The design ethos was to provide a ‘bare-bones’ system which was relatively easy to understand, and we provided each trial operator with a single one-to-one training session on the use of the system. These training sessions lasted between two and four hours (depending upon technical ability) and this seems to have been sufficient. Initial configuration files were created and tested in the presence of each operator. The approach encouraged and enabled operators to learn about their transmission system, and the system’s initial simplicity encouraged some operators to add their own monitoring and control systems.

11.6 The type 1 (single transmitter) trial operators appear to have had very few problems during the initial trial period, and the platform has proven to be very reliable in service. Most of the trials have not needed to do much more than make changes to the multiplex configuration when required (e.g. to add new audio services to the multiplex).

11.7 Although the transmitter equipment racks were designed to operate for the initial 9 month trial period, it is expected that they will continue to operate into the extension period providing the environment in which they are installed is clean and has adequate airflow to dissipate the exhaust heat from the amplifier.


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Figure A2: two of the 12RU trial racks undergoing functional testing


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Section 12

12 Lessons: Single Frequency Network trials Overview

12.1 Single Frequency Network (SFN) operation required considerable additional attention compared to the ‘set and forget’ nature of the single transmitter trial systems. The software patches to enable SFN operation had not been used in production previously, so additional work was needed to identify and validate suitable hardware combinations and software configurations.

12.2 An ongoing test of running the ensemble multiplexer in a cloud service indicated that full duplication with separate infrastructures and connectivity would be required to prevent extended unplanned outages. It was also considered that such a solution would place too much reliance on third parties and make it difficult to identify the location and cause of connectivity issues. Relying on third party infrastructure can also potentially increase susceptibility to direct or indirect Denial of Service attacks.

12.3 Therefore, it was decided that the multiplexer should run at a nominated principal, or master, transmitter site and that each slave transmitter site could also take on the multiplexing role if needed.

12.4 One of the SFN trials connected their sites to the Internet via an EoFTTC service, and also cross-connected them with a fixed microwave link to provide resilience against circuit failure. This approach also extended the LAN to both sites. This additional link proved to be very useful for fault investigation and resolution. Each of the two sites could receive streams from the source encoders, even though most of these streams were configured to just send to a single destination. Either site could additionally be used as an ingress route to pull alternative sources such as web streams in case of temporary failure in the primary feed.

12.5 The other SFN trial encountered difficulty in provisioning suitable connectivity for supporting SFN operation. An attempt to connect a transmitter to the public internet via a domestic cable internet service which was extended onwards to the site by WiFi seemed to work in single transmitter mode, but the stability of the SFN operation has not been satisfactory. Both SFN trials were provided with identical software and hardware, with the exception of the power amplifiers as these were provided by two different suppliers.

12.6 The transmission racks were identical to those used by single transmitter trials with the exception of an additional timing module fitted inside the SDR and a slightly different version of the modulator and Universal Hardware Driver software. The module also required a Global Positioning System aerial to be installed on each site, as the timing modules utilise GPS to discipline the reference oscillators such that they have long-term sympathy with all other transmitters in the group.

12.7 Originally, GPS modules were procured from the same supplier as the radio unit, but maintaining synchronisation using these modules was initially found to be problematic. Due to project timescales an alternative solution was sought. We therefore used alternative GPS modules based on a commercial RF module. These needed to be hand-soldered to an open source daughterboard specifically designed by the Open Digital Radio group to enable it to be interfaced to the radio unit. Debugging of the SFN timing has been an on-going process, and the problem with


23

the original ‘stock’ timing modules was subsequently found to be due to a software issue, and was resolved.

12.8 The alternative module performed well during an issue affecting the GPS satellite constellation. The decommissioning of GPS satellite SVN23 on 26 January 2016 caused problems with the synchronisation of some DAB transmitters. The operational small-scale SFN trial was not affected – possibly because the timing devices can utilise signals from other Global Navigation Satellite Systems in addition to GPS.

Figure A3: Software defined radio board with timing modules 12.9 The most significant issue with SFN operation during the trials was a lack of long

term synchronisation stability. Although the RF carrier frequency was tightly controlled by the GPS-disciplined oscillator references, the RF launch delay time appeared to change suddenly by around 400μs after (on average) six days of continuously synchronous operation. This could be prevented through a pre-emptive reset of the modulators during maintenance windows.

12.10 This difference in the launch time of the transmitted data is almost double the time difference which DAB Transmission Mode 1 is designed to withstand. This resulted in a loss of network gain, and destructive inter-symbol interference in a ‘mush zone’ where the transmitter coverages overlapped. The loss of correct synchronisation therefore led to periodic reception problems within this area.

12.11 The investigation work around this timing issue has taken a considerable amount of effort. However, we now believe that the problem has been resolved after significant refactoring of source code by Open Digital Radio. A new build of the platform for SFN will be released by Ofcom to the two SFN trials during September 2016.

12.12 One potential issue related to SFN operation of small-scale multiplexes is that the capital and operating costs are broadly proportional to the number of transmitters within the SFN. As discussed earlier, higher grade (and higher cost) circuits may also be required for new transmitters in an SFN, which would further increase costs.


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Section 13

13 Lessons: On-channel repeater trial About on-channel repeaters

13.1 Practical on-channel repeaters (OCRs) for DAB were first described in a BBC Research & Development paper12 from September 2005. Such devices can be used in conjunction with a main transmitter to form a (largely overlooked) type of Single Frequency Network. They can extend coverage in the same way as a regular SFN transmitter site, but do so by receiving and transmitting on the same frequency.

13.2 OCRs do not require distribution telecoms circuits. So although the initial equipment costs are higher than for more conventional network architectures, they can potentially deliver significant cost savings over the life of the plant. They can also be used in locations where providing connectivity might be problematic or prohibitively expensive.

13.3 OCRs require a strong, reliable incoming ‘donor’ signal, as well as considerable RF isolation between the receiving and transmitting aerials at the OCR site. Local echoes caused by reflections from nearby buildings and terrain are removed from the signal during conditioning, which is carried out by dedicated digital signal processing circuits. The process is adaptive and can deal with environmental changes which may cause the echo characteristics to change.

13.4 The need to achieve quite high levels of isolation between the receiver and transmitter in the repeater unit does place constraints on where such an installation is practical. GPS disciplined oscillators are not required as the donor transmitter provides an adequate reference.

Initial investigations

13.5 As there is very little literature available about how these units actually perform in service, we decided to carry out practical trials of the OCR concept as part of the small scale DAB trials.

13.6 Ofcom engineers obtained a sample of the only complete and commercially available OCR unit found during market testing. This was evaluated during the project preparation phase at Baldock Radio Station in Hertfordshire. A DAB test transmitter comprising of an Odroid U3 module and a B100 software defined radio was established inside a cabin on an enclosed area of the estate. This fed a low power amplifier and mask filter and radiated from an end-fed dipole aerial mounted on a telescopic trailer-mounted mast. The arrangement provided 1 watt ERP on block 11A and this provided the donor signal for the OCR.

13.7 The OCR was installed in another compound around 0.5 km away. The OCR site had approximately 50m of separation between a cardioid transmitting aerial and a seven element yagi aerial (used for receiving the signal from the donor transmitter). The separation distance need not be so great if physical obstructions can be used to provide attenuation of stray radiation in the path between the two aerials.

12 http://www.bbc.co.uk/rd/publications/whitepaper120

http://www.bbc.co.uk/rd/publications/whitepaper120


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13.8 The isolation was optimised using a spectrum analyser connected to both aerials, and the transmitting mask filter was left in circuit whilst the aerial positions were optimised. The power received by the donor aerial was then measured. Isolation in excess of 90dB was achieved. A reduction in the high levels of local echoes caused by a chain link fence was achieved by increasing the donor aerial height. The optimisation process enabled the unit to operate at its full rated power output of 100 watts RMS.

13.9 Initial checks for receiver blocking (ACI) were carried out, with particular attention paid to reception of the in-use adjacent DAB block (10D). As reception was not impaired (because the signal from 10D was very strong locally), the transmitter was able to operate for extended periods during which drive test surveys were conducted.

OCR deployment during the trials

13.10 Because of the very encouraging test results, the OCR was selected for further testing at one location during the stakeholder trials. The trial site was a tall church bell tower, which is not an ideal structure as several technical requirements which could not be fully met. The separation distance between the aerials was less than optimal, and the desired 7-element receiving yagi aerial could not be used due to aesthetic and practical concerns. Alternative aerials were sourced, but these were found not to provide the predicted isolation and were later found to have a design defect. Replacement of these did not significantly improve the situation and the transmitter was operated at 50 watts ERP for the remainder of the trial period in order to maintain a sufficiently stable isolation margin.

Possible alternative applications for OCRs

13.11 The OCR architecture may offer the technical potential for other new DAB applications, such as a novel form of studio-to-transmitter distribution architecture (i.e. providing a feed to an operator’s ‘primary’ DAB transmitter site from a studio or multiplexing centre without the need for IP circuits or other data links). In this application, a directional and relatively low-power small scale DAB transmitter could be used at the studio site, with the signal being directed towards the primary transmitter site, where an OCR transmitter could provide the principal coverage for the service.

13.12 The use of opposite slant (or circular) polarisation could deliver some additional isolation if used at the donor transmitter, but such an arrangement could increase the risk of blocking due to the angle of radiation on some bearings.

13.13 The OCR test bed was demonstrated during a stakeholder technical event as a proof of concept, and many attendees recognised the benefit of feeding the ‘best server’ transmitter from a low power source located elsewhere. In this situation, the donor transmitter can also provide local coverage (as the OCR transmit aerial would generally be directed away from the donor transmitter). This is a very spectrally efficient approach by virtue of it using the same frequency block, and it therefore has no spectrum opportunity cost. Further isolation gains are technically possible by alternating the polarisation between the receiver and transmitter. While all current UK DAB services use vertical polarisation, opposite slants or circular polarisation could potentially be employed between master and slave stations.

1

Small scale DAB trials Annex 3: Summary of technical feasibility studies on

frequency planning

Research Document


Small scale DAB trials Annex 2: Summary of technical feasibility studies on frequency planning

2

Contents

Section Page 1 Summary of frequency planning studies 3

3

Section 1

1 Summary of frequency planning studies Frequency availability is key to deployment of small scale DAB

1.1 A key technical enabler of the current small scale DAB trials – and for any wider roll-out of small scale DAB in the future – is that a suitable quantity, and type, of transmission spectrum needs to be available for small scale use.

1.2 Work carried out for the DCMS Digital Radio Action Plan (DRAP) during 2011 indicated that coverage of the existing local DAB layer was interference limited (i.e. the coverage of a specific multiplex tends to be limited by interference from other multiplexes using the same frequency elsewhere) rather than being noise limited (i.e. where the coverage area extends to where the signal level drops below the level of noise inherent in receivers).

An initial study indicated that additional spectrum will be required

1.3 When small scale DAB was first being considered, it quickly became apparent that additional spectrum would be required to accommodate the new services. We therefore took the opportunity to carry out an initial study to identify the potentially available spectrum for small scale DAB in the Manchester area (which is an area where there is a high level of demand from community radio, and where changes to the frequencies used by the existing local DAB multiplexes were also being planned).

1.4 The purpose of the Manchester study was to quantify what spectrum was available, and how many small local and community services in digital form this spectrum resource might support. We assumed that existing transmission sites would be used, and that these would form a number of single frequency networks (SFNs). We found that, overall, fewer sites would be required for DAB than for analogue radio, although slightly higher powers were proposed from each site (50 or 100 watts ERP for DAB rather than the 25 watts ERP typically used by analogue community radio services).

1.5 Three blocks of spectrum were identified as being of potential use in the Manchester area, and these would have accommodated the existing analogue services. However, it was also apparent that these frequencies were the only ones available over a wider area which included Liverpool, Preston and Stoke-on-Trent, and that more spectrum would therefore be required to implement small scale DAB across the wider region.

Some spectrum in Band III is very lightly used at present

1.6 In order to facilitate the small scale DAB trials, Ofcom carried out separate technical work to identify whether additional spectrum could be made available. All modern DAB receivers are able to tune to a band of spectrum between approximately 174 MHz and at least 230 MHz (also known as blocks 5A to 12D) within VHF Band III, which is internationally allocated to broadcasting. With agreement from most neighbouring countries, the UK also uses Band III spectrum for private business radio services (also known as Private Mobile Radio, or PMR). These services were introduced to the band following the closure of the UK’s VHF television services in the 1980s. In addition, other counties also use the band for other secondary services


4

such as Programme Making and Special Events (PMSE) equipment and Assisted Listening Devices (ALDs).

1.7 Band III was completely re-planned at the International Telecommunications Union regional planning conference held in Geneva in 2006 (Ge06). As part of this re-planning, the UK agreed not to seek protection of business radio services in a part of Band III known as ‘sub-band II’. Business radio services are more vulnerable to interference than the DAB and digital terrestrial television (DTT) services which are already carried in these bands in neighbouring countries. Had the UK continued the use of business radio in both sub-band I and sub-band II, this would have impeded the implementation of digital broadcasting in mainland Europe. Following the conference, sub-band II business radio users in the UK were advised of the likely increase in interference and advised to migrate to sub-band I or to alternative spectrum.

1.8 Sub-band II is now very lightly used, and in 2015 Ofcom gave the remaining users notice to vacate the band within five years. This will make six further frequency blocks available for small scale DAB. However, we carried out a technical assessment which indicated that continuing use by business radio until 2020 will mean that parts of north west England and the English midlands will have limited access until remaining business radio services have migrated out. The sub-band II blocks could be supplemented by any available frequencies within the existing local DAB spectrum.

1.9 The figure below illustrates how the usage of Band III looked before the Ge06 conference, and how it might look in 2020.

Figure A1: Plan of UK Band III usage

The additional spectrum could be suitable for small scale DAB, but would be subject to some constraints

1.10 As mentioned above, the UK has already partially vacated business radio from sub-band II in order to enable the roll-out of DAB and DTT in mainland Europe. Neighbouring countries therefore now have broadcasting allocations on these frequencies which have protected rights recorded in the Ge06 Plan. Consequently, any UK roll-out of small scale DAB will not be able to impede the implementation of these services in neighbouring countries.

5

1.11 The UK rolled out most of its existing DAB some years before neighbouring countries. The final requirements for DAB spectrum by Belgium, France, Ireland and the Netherlands are not yet fully known and may not be for several years. Where DTT in the VHF band was planned at Ge06, we now expect that these allocations will instead be used for DAB. It is within this changeable landscape that small scale DAB in the UK will need to be planned.

1.12 However, there is an increasing interest in small scale DAB in Europe, and this may provide opportunities to standardise usage in a particular part of the spectrum.

1.13 Based on neighbouring countries’ existing Ge06 implementation rights and subsequent developments, we expect that the following areas could be subject to significant levels of interference (particularly to mobile DAB reception), on some or all frequency blocks in sub-band II:

• SW Scotland (Dumfries & Galloway, Ayrshire, Isle of Arran, Mull of Kintyre);

• Northern Ireland;

• West and north Wales;

• Southern & Eastern parts of England (including some or all of Cornwall, Devon, Dorset, Hampshire, the Isle of Wight, Sussex, Surrey, Kent, Essex, Suffolk, Norfolk & London).

1.14 While outside the scope of our technical studies, we expect similar issues on the Isle of Man and the Channel Islands.

1.15 Small scale DAB would need to be implemented on the frequency blocks which are available in each area on a case by case basis. However, as neighbouring countries’ frequency plans evolve it is likely that some small scale DAB services could need to change frequency to accommodate this. They should be implemented in a technical manner that allows this.

1.16 When planning frequencies for analogue community radio, less restrictive planning parameters have been used than for local and national radio in order to maximise the number of services which can be provided. Ofcom believes that the same planning parameters already used for local and national DAB will also probably need to be applied to small scale DAB. However, for DAB there are two licensed coverage levels, classed as ‘mobile’ and ‘indoor’. Within the indoor coverage zone, mobile coverage will also be available. Therefore, one option may be for us to plan and protect only indoor coverage. This would also allow more frequencies to be usable, particularly where interference from neighbouring countries is an issue.

Our second study concluded there would be sufficient spectrum to enable existing analogue services to move to DAB in most areas, although some areas of congestion remain

1.17 Ofcom carried out a second technical study (available as Annex 41) to identify whether the six additional blocks of sub-band II spectrum might be sufficient to potentially provide a technical opportunity for existing analogue-only community and





6

local radio services to be carried on DAB. Where this was not possible the study considered whether any available blocks within the existing local DAB spectrum could be used instead.

1.18 The study assumed that the analogue broadcasters’ existing transmission sites would be used for small scale DAB, and found that:

• In all but a few locations six blocks of spectrum would be sufficient to create notional multiplexes which could accommodate all of the existing non-DAB services. The areas of congestion identified were:

o North Somerset and south east Wales;

o The east midlands of England (where no local DAB frequencies are available either);

o Areas to the south of Manchester.

• Some additional benefit could also be gained by using the more efficient DAB+ coding, as more services could be carried on a single multiplex;

• Indoor coverage would generally be protected from interference; however mobile coverage would often be reduced during periods of enhanced propagation (such as high pressure weather conditions);

• Incoming international interference would be a significant issue in numerous locations;

• Using powers of up to 100 watts and directional transmitting antennas, robust indoor coverage could be achieved while keeping levels of outgoing interference to neighbouring administrations to generally acceptable levels;

• Overall fewer transmitters would be required for the notional digital multiplexes than for the individual analogue services they might carry.

• While potential nominal coverage areas were found for all of the existing analogue services, the study did not investigate the potential for small-scale DAB in areas where there are no existing community or analogue-only radio stations. Further research would be required in order to produce a plan which will allow small scale DAB to be implemented in all areas.

There are other issues that require further consideration when developing a plan for small scale DAB deployment

Interference to local and national multiplexes 1.19 New DAB transmitters have the potential to cause an effect known as ‘adjacent

channel interference’ (ACI) or ‘blocking’ to reception of multiplexes which provide a service in the vicinity. In order to minimise this effect, the UK has endeavoured to co-site DAB services as far as possible. However, the different network topologies required for local and national services means this cannot always be achieved and in some cases mitigation measures are required. This mitigation is based on the premise that operator of the new multiplex resolves any issues, and mitigation is not applied retrospectively. Mitigation can be achieved in a number of ways, including:

7

• Site sharing, or the use of a site close to the ‘victim’ service(s);

• Moving the site to a location away from population and major roads;

• Moving the site to an area where the ‘victim’ service signal level is high;

• Adjusting transmission parameters (e.g. using lower powers or directional antennas)

• Providing a co-sited low power transmitter carrying the ‘victim’ service(s)

1.20 As any future small scale multiplexes are expected to have smaller coverage areas than existing multiplexes, the small scale transmitter network topologies would be different to their local and national counterparts, and this may lead to blocking issues. During the trials, low transmission powers were used, which helped to minimise these effects, and we didn’t find significant ACI issues at the 10 trial locations. This may have been due to the small scale trials all being located in areas where existing DAB signal levels are fairly high. However, it was noted that the trial services were sometimes impacted by the higher power transmitters used by existing national and local transmitters already operating within their service areas – this is an effect known as ‘reverse ACI’.

Further work

1.21 One complexity of the frequency planning process is how to define the area served by a multiplex and to identify those services which will be carried on it. Each analogue local or community service has a distinct service area derived from the transmission parameters it uses. In contrast, a DAB multiplex delivers the same coverage area to every service carried by it. To avoid disenfranchisement of analogue listeners, the digital coverage would need to extend to serve all of the analogue services carried by it. This may lead to an alteration of the original localness of the individual programmes carried. Significantly larger service areas could be achieved by carrying a service on geographically adjacent multiplexes. The study found that, in the majority of areas, frequency availability means that only one small scale DAB multiplex could be planned.

1.22 Due to the very limited number of frequencies available it would be very easy to allocate them all in the first sequence of licensing. This could mean that frequencies would not be available in adjacent areas for future small scale DAB services.

1.23 One way to avoid this would be to define a whole UK coverage plan identifying a frequency for all areas which could be pre-coordinated with neighbouring countries. The downside is that frequencies would be allocated to areas where no service operates.

Small scale DAB trials Annex 5: Summary of service provider survey results

Research report


About this document During August 2016 we invited radio stations on small scale DAB multiplexes to complete an online survey which asked about their experiences during the trial, and their views on the future prospects for small scale DAB. Of the 69 stations invited to complete the survey, 40 did so, a response rate of 58%. This Annex contains a sub-set of the service providers’ survey responses. In order to preserve respondent confidentiality, we are not publishing survey responses which could be personally identifiable, or which may be commercially sensitive. We also carried out a similar survey of trial multiplex operators. Due to the small sample size and confidentiality issues, we are not publishing response summaries for the separate multiplex operator survey.

17.95% 7

2.56% 1

7.69% 3

15.38% 6

33.33% 13

2.56% 1

Q5 You may be aware that the Small Scale

DAB trial was originally licensed for a 9-

month period. Ofcom has subsequently

extended the trial licenses for a further two

years. During the initial 9-month trial period,

approximately how much did you pay for

carriage of your service on the Small Scale

multiplex per month? If your service is on

more than one trial, please supply an

approximate average for a single service.

Answered: 39 Skipped: 2

No carriage

costs charge...

£1 to £49 per

month

£50 to £99 per

month

£100 to £199

per month

£200 to £499

per month

£500 to £999

per month

More than

£1,000 per...

Rather not say

Other (please

specify)

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Answer Choices Responses

No carriage costs charged by multiplex operator

£1 to £49 per month





1 / 7

Small Scale DAB trials survey - Service Providers

2.56% 1

5.13% 2

12.82% 5

Total 39

More than £1,000 per month

Rather not say

Other (please specify)

2 / 7


40.54% 15

32.43% 12

24.32% 9

2.70% 1

0.00% 0

0.00% 0

Q8 What was your general experience of

negotiating carriage on the Small Scale

Multiplex(es)?


Total 37

Very easy

Easy

Neither easy

nor difficult

Difficult

Very difficult

Don’t know

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%


Very easy

Easy

Neither easy nor difficult

Difficult

Very difficult

Don’t know

3 / 7


72.97% 27

8.11% 3

18.92% 7

Q9 Now that the Small Scale licences are

being extended, do you anticipate that your

service or services will likely continue to be

carried on Small Scale DAB?


Total 37

Yes

No

Don't know

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%


Yes

No

Don't know

4 / 7


40.74% 11

44.44% 12

0.00% 0

11.11% 3

3.70% 1

Q10 Have you agreed changes to your

carriage terms(s) for the extended trial

period?


Total 27

Yes – Carriage

costs will...

Yes – Carriage

costs will...

Yes – Carriage

costs will...

No - costs for

extended per...

Don’t know

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%


Yes – Carriage costs will increase

Yes – Carriage costs will remain the same

Yes – Carriage costs will decrease

No - costs for extended period have not been agreed yet

Don’t know

5 / 7


8.33% 1

50.00% 6

16.67% 2

8.33% 1

8.33% 1

8.33% 1

Q11 Approximately how much are your new

carriage costs per month increasing by for

the extended trial period?


Total 12

£1 to £50 per

month increase

£51 to £100

per month...

£101 to £200

per month...

£201 to £500

per month...

More than £501

per month...

Rather not say

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%


£1 to £50 per month increase




More than £501 per month increase

Rather not say

6 / 7


56.76% 21

13.51% 5

29.73% 11

Q14 It is likely that a permanent Small Scale

DAB licensing framework will be introduced

in the future. Do you feel that the Small

Scale DAB concept offers a commercially

sustainable method of distribution for your

service?


Total 37

Yes

No

Don't know

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%


Yes

No

Don't know

7 / 7


Ofcom

DAB RF Sensitivity Measurements

by

DTG Testing Limited

Dated: 8th April, 2016

Alex Buchan (Principal RF Engineer) DTG Testing Ltd

5th Floor, 89 Albert Embankment London, SE1 7TP

Email: [email protected] Tel: +44(0) 207 840 6500

www.dtgtesting.co.uk

mailto:[email protected]

1 Confidential

Contents

1 Executive summary ........................................................................................................................................... 2

2 Implementation .................................................................................................................................................. 3

2.1 Test plan ..................................................................................................................................................... 3

2.1.1 Setup ........................................................................................................................................................... 3

2.1.2 Procedure .................................................................................................................................................. 4

2.2 Measurements ........................................................................................................................................... 4

2.2.1 Scope .......................................................................................................................................................... 4

2.2.2 Frequencies tested .................................................................................................................................. 6

3 Results .................................................................................................................................................................. 6

4 Conclusion .......................................................................................................................................................... 8

Appendix A – Details of test stream ..................................................................................................................... 9

Appendix B – Results for radiated testing .......................................................................................................... 10

2 Confidential

1 Executive summary

Ofcom have commissioned a programme of radiated tests to understand the minimum RF sensitivity performance for a sample of 20 DAB receivers either supplied by Ofcom or which had previously successfully undergone DAB tick mark conformance testing. The objective of the programme was to investigate the following:

a) the RF sensitivity across a range of seven VHF Band III frequencies, six of which are 7D, 8A, 8B, 9A, 9B and 9C as used in the small scale DAB trial, along with 12B which is currently used for the BBC national multiplex; and

b) the performance across 20 DAB receivers from the DTG DAB Receiver Zoo selected primarily on sales data.

The testing was carried out over two lab days at the DTGTL premises in Vauxhall on the 22nd and 23rd of March 2016. The results showed that the large majority of measurements exceeded the minimum requirements specified for the DAB tick mark. This can be seen from the CDF plot for the radiated testing (18 out of the 20 radios) where between 82% and 100% of measurements (depending on the channel being tested) were better than the minimum threshold. These were from measurements made on mainly domestic radios (13 out of 20) but which also included an AV receiver, a Hi-Fi unit, and 3 handheld radios. In addition, conducted sensitivity measurements were made on 2 in-vehicle radios which passed the requirements across all the frequencies tested. This shows that although the frequencies tested as part of this programme are not in widespread use in the UK currently, products are still being designed to cater for their usage. Further work may be to expand the number of products tested and include a larger sample of cheaper models, supplemented with sales data, which may not have been submitted for tick mark testing. This may highlight the potential range in performance of products in the market.

3 Confidential

2 Implementation

2.1 Test plan The procedure and setup used during testing was the same as that used for RF Sensitivity measurements in the DAB tick mark specification1, for which DTGTL holds ISO17025 accreditation and against which it has tested over 200 DAB radios against to date.

2.1.1 Setup

The diagram below shows the generic setup for DAB RF sensitivity testing in a GTEM cell as used by DTGTL.

3.05

met

re

1.73

2m

Marker

0.5 metre clear to

antenna tip

≥ 800 mm PSU lead

(when req’d)

Non conducting table surface

Excesslead

Septum plate

Acoustic pickup or microphone with fibre optic relay

EUT receiver antenna

Audio signal relay box (if required)DAB PlayoutCalibrated RF Signal GeneratorTo RF Input

of GTEM

Figure 1 Radiated sensitivity test setup

The RF signal generator used is a Rohde & Schwarz SFU which allows playback of DAB ETI files at frequencies and signal levels selectable by the user. The ETI file used for testing is as specified in Appendix A of this report and was provided to DTGTL by Digital Radio UK (DRUK) in order to carry out tick mark testing.

The audio from the radio under test is relayed from the GTEM cell to a XENYX1002FX mixing desk via a microphone positioned at the viewing window of the cell. A pair of headphones is used to listen to the output of the mixing desk.

The RF output of the SFU is connected via a 3m long N-Type cable to a power splitter which is positioned just before the input to the GTEM cell. Two identical N-Type cables are connected to the output of the power splitter, one providing the input to the GTEM cell and the other connected to the input of a Rohde & Schwarz FSH4 spectrum analyser. As the RF signal level at the input to the

1 http://www.getdigitalradio.com/industry/technical-documents/

http://www.getdigitalradio.com/industry/technical-documents/

4 Confidential

GTEM cell is used to calculate the field strength inside based on GTEM cell calibration data, a spectrum analyser is used to ensure that an accurate reading is taken.

During the testing, sensitivity measurements were made on three handheld radios where the antenna is the set of headphones provided with the radio. The way these were tested was by a person inside the GTEM cell wearing the headphones. The reason for this was so that the effect of the person’s body on the antenna/headphones could be taken into account when measuring the sensitivity.

For in-vehicle radios a conducted test is done as per the DAB tick mark specification. This is because of impracticalities in trying to set up a representative radiated test scenario for a radio being used in a vehicle with a glass mounted or mag-mount antenna. The conducted test consists of the RF output of the R&S SFU being connected directly to the input of the in-vehicle radio.

2.1.2 Procedure

The minimum RF sensitivity is measured using onset of impairment method (OOI) described in the DAB tick mark specification.2 The OOI test calls for a 1 kHz audio signal tone to be monitored for acoustic quality over a 30 second period and for the detection of audio impairments.

An impairment is defined as any recognisable deviation from a constant amplitude, constant frequency 1 kHz audio tone; for example audio drops or gaps, or bursts of non-1 kHz signal tone – sometimes called “burbles”, “tweets”, “chirps” or “birdies”.

The OOI method specifies that is if there are no more than three impairments observable in a 10 second time period averaged over 3 cycles (30 seconds), then the receiver has passed the test.

The ‘Sine’ service of the ETI file plays out a 1 kHz tone which is used to assess audio glitches as described above.

A summary of the test steps are:

1) Carry out a check to verify the test setup is working as expected and that the radio can play the 1kHz tone without any problems – if so the tests can start

2) Set the generator to the required frequency and signal level 3) Set the analyser to the required frequency 4) Tune the radio and ensure the 1kHz tone can be heard without any impairments 5) Reduce the RF signal level using the signal generator until the OOI conditions are met 6) Record the RF signal level at the last point before the OOI limit was reached – this is the

minimum RF sensitivity 7) Repeat the steps for the next frequency to test.

2.2 Measurements

2.2.1 Scope

The scope of this proposal is taken from an email to DTG on 27th April 2015 from Paul White at the Ofcom Spectrum Policy Group. This outlines the following requirements:

2 http://www.getdigitalradio.com/industry/technical-documents/

http://www.getdigitalradio.com/industry/technical-documents/

5 Confidential

x Minimum RF sensitivity measurements on seven Band III frequencies of 7D, 8A, 8B, 9A, 9B, 9C and one other frequency (to be confirmed by Ofcom) that is currently covered as part of the tick mark testing;

x Tests are to be carried out on a minimum of 20 DAB receivers over 2 lab days; x The DAB receivers will be selected from the DTGTL DAB receiver Zoo and will have

passed tick mark conformance testing; and x The selection of models from the tick mark tested radios will be based upon highest sales

volumes (Ofcom to provide sales data).

In the end, Ofcom provided 7 radios from their test facility at Baldock. The remaining 13 were taken from the DTGTL receiver zoo where 7 of these were specifically listed by Ofcom and the remaining 6 out of the 13 were to be chosen by DTGTL. There were no particular criteria set by Ofcom for choosing the remaining 6 other than that anything too ‘niche’ should be avoided and that preferably the sample should contain an in-vehicle unit and a Hi-Fi unit. All of the 13 receivers taken from the DTGTL zoo had previously passed the DAB tick mark requirements.

The final set of the receiver types used for the tests and the test ID given to them is shown below.

Table 1 List of receivers used for testing

At the time of writing the DTGTL DAB Receiver Zoo consists of 77 radios that have been tested as part of tick mark conformance. These radios are a combination of domestic, in-vehicle and handheld radios as well as AV receivers with DAB tuners. Previous results from testing can be easily referenced in order to compare and verify receiver stability.

Test ID DAB receiver typeRX1 DomesticRX2 DomesticRX3 DomesticRX4 HandheldRX5 DomesticRX6 DomesticRX7 DomesticRX8 DomesticRX9 DomesticRX10 DomesticRX11 DomesticRX12 DomesticRX13 HandheldRX14 HandheldRX15 DomesticRX16 DomesticRX17 Hi-FiRX18 AV ReceiverRX19 In-vehicle head-unitRX20 In-vehicle head-unit

6 Confidential

2.2.2 Frequencies tested

Minimum sensitivity tests were carried out on each receiver for the following channels:

Table 2 List of frequencies tested

Channels 7D to 9C were selected by Ofcom due to the fact they are used as part of the small scale DAB trial they are undertaking. Channel 12B was chosen by DTGTL as it is used by the BBC national multiplex and can provide a comparison between a results for a frequency currently used in the UK against results for frequencies used in the small scale trial.

3 Results

The results show that on average the receivers comfortably met the minimum sensitivity requirements as specified in the DAB tick mark, across all of the frequencies tested. This can be seen in Table 3 below.

Table 3 Average measured radiated sensitivity

Individual results for the receivers can be seen in Appendix B of this report but out of the 18 receivers that underwent radiated sensitivity measurements, 4 failed to meet the minimum requirements on some of the frequencies tested. These were receivers RX1, RX2, RX4 and RX5.

Channel Frequency (MHz)7D 194.0648A 195.9368B 197.6489A 202.9289B 204.649C 206.352

12B 225.648

Channel Frequency (MHz)

PASS/FAIL target threshold

(dBµV/m) for OOI test including measurement

uncertainty

Average measured radiated sensitivity

(dBµV/m)

Difference between

average and pass/fail (dB)

7D 194.064 35.5 29.1 -6.48A 195.936 35.6 29.1 -6.48B 197.648 35.6 27.7 -8.09A 202.928 35.9 29.2 -6.79B 204.64 35.9 29.4 -6.69C 206.352 36.0 29.4 -6.6

12B 225.648 36.8 30.2 -6.6

7 Confidential

The CDF plot below shows what this means in terms of percentages of receivers that met requirements across each frequency tested.

Figure 2 CDF of measured radiated sensitivity

Similarly for the conducted tests carried out on the in-vehicle radios, the receivers were able to meet the requirements although RX20 only marginally passed the requirement for channel 9A by 0.3dB. As only 2 radios were tested in this way the individual results are given below in Table 4.

8 Confidential

Table 4 Measured conducted sensitivity

4 Conclusion

Overall, the large majority of measurements exceeded the minimum requirements specified for the DAB tick mark. This can be seen from the CDF plot for the radiated testing (18 out of the 20 radios) where between 82% and 100% of measurements (depending on the channel being tested) were better than the minimum threshold. These were from measurements made on mainly domestic radios (13 out of 20) but which also included an AV receiver, a Hi-Fi, and 3 handheld radios. In addition, conducted sensitivity measurements were made on 2 in-vehicle radios which passed the requirements across all the frequencies tested.

This shows that although the frequencies tested as part of this programme are not in widespread use in the UK currently, products are still being designed to cater for their usage. Further work may be to expand the number of products tested and include a larger range of cheaper models, supplemented with sales data, which may not have been submitted for tick mark testing. This may highlight the potential range in performance of products in the market.

ChannelFrequency

(MHz)

PASS / FAILtarget

threshold(dBm) for conducted

test*

PASS/FAIL target threshold (dBm)

for conducted test including

measurement uncertainty

RX19 RX20

7D 194.064 -97.7 -98.6 -100 -100.28A 195.936 -97.7 -98.6 -100 -99.58B 197.648 -97.7 -98.6 -100.5 -99.89A 202.928 -97.7 -98.6 -99.8 -98.99B 204.64 -97.7 -98.6 -99.5 -999C 206.352 -97.7 -98.6 -99.7 -99.5

12B 225.648 -97.7 -98.6 -99.5 -99.3

Level at which OOI test Impairment

recorded (dBm at input to receiver)

9 Confidential

Appendix A – Details of test stream

DRAP-TEG-TESTSTREAM-001_V0.5.eti

This file contains a 120 minute long ETI (NI) test stream and contains the following sub-channels. (Note that there will be a stream discontinuity at the end of the 120 minute play out file, which will create an audible “glitch” artefact. The stream may be restarted to ensure the stream provides due continuity during the test period.).

The DLS string in SID C000 contains the code 0x0B (end of headline) at the 32nd position and 0x0A (preferred line break) at the 15th position and 0x1f (preferred word break) at the 12th position; and code 0x1f every eight characters from position 33 to the end.

LABEL: DRAPMUX1 EID: C555

* The music file is AKMusic AK033-“Good Time Grooves - Jazz n Funk”, track 11 “newyorkskyline”

Service label / SID

Short Label Bit rate / Codec Audio Content DLS (note: this is not required for in-vehicle receivers)

Sine / C000 Sine 128k / MP2/

EEP-3A 1kHz tone “ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789£%& !."(),”

OOI Music* / C001

OOIMusic 128k / MP2/ UEP-3

Royalty free music*

“OOI Music Source 128k MP2 UEP-3 Stereo”

AHBGCFDEEDFCGBHA/ C002

ABCDEFGH 128k / MP2 1.5kHz tone “MP2 128kbps 1.5kHz tone”

IPJOKNLMMLNKOJPI / C003

IJKLMNOP 96k / AAC 2kHz tone “AAC 96kbps 2kHz tone”

QXRWSVTUUTVSWRXQ / C004

QRSTUVWX 96k / AAC 3kHz tone “AAC 96kbps 3kHz tone”

10 Confidential

Appendix B – Results for radiated testing

Date post:	16-Apr-2017
Category:	Technology
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Final report small scale dab OFCOM (UK)

Technology