No, your presenter is not “drinking the iBiquity Kool-Aid” IBOC / HD Radio TM : Engineering...

No, your presenter is not “drinking the iBiquity Kool-Aid”

IBOC / HD RadioTM : Engineering ConcernsAaron Read (G.M. : Public Radio for the Finger Lakes)

Already decided HD RadioTM is right for you? Here’s a look at

what you’ll need to do.

See also : http://www.hdradio.com and http://www.dreinc.com

Essential Questions

This session is not about whether or not your operation can deal with the various issues involved with HD Radio.

We’re here to look at what’s involved with the engineering behind installing HD Radio at your facility or facilities.


Are you an AM station?

If you don’t have an FM station, be advised: we’re not going to talk much about AM IBOC. It has a lot of problems and the entire future of AM

IBOC is arguably still in question. Digital sidebands cause significant 1st adjacent

interference – nighttime skywave means that interference goes 1000’s of miles.

Audio quality improvements are impressive for music but sounds pretty “crunchy” for news/talk.


What is HD Radio?Hint: the “HD” doesn’t stand for anything!

These sidebands do put some more RF energy on the adjacent channels, so IBOC can cause 1st-adjacent interference issues.

Backwards-compatible, existing analog radios ignore the digital (sounds like “white noise”)

HD Radio is a brand name by the creator: iBiquity Technical term is IBOC : In-Band/On-Channel.

Uses digital sidebands on your existing analog signal.


Is HD Radio required?

No – it is currently a hybrid system: both analog and digital. Fully backwards-compatible, and (by FCC R&O) optional for stations to migrate. All-digital system is possible, but FCC not allowing it. All-digital does hold promise for more data b/w and

less interference issues.

Note that eventually it’s likely the marketplace / listeners will demand you migrate to HD.


What is HD Radio?Also known as “IBOC”

IBOC-equipped radio will first play the analog audio feed immediately, then begin buffering the audio data. This results in approx. 7 second delay of program audio.

After a few seconds, the radio will “blend” to the digital audio feed. Make sure your analog & digital audio feeds are time-synched! Digital audio uses the HDC codec. Details are proprietary, but

rumored to be a variant of the impressive AAC codec. If the HD signal is lost, the radio blends back to analog.


Simple FM IBOC Transmission Topology – All IBOC Gear at Transmitter Sitediagram courtesy of The IBOC Handbook, page 401


FM IBOC Transmission Topology – with Exporter and Exgine Modulesdiagram courtesy of The IBOC Handbook, page 405


FM IBOC Transmission Topology – with Exporter & Exgine Modules, plus Importerdiagram courtesy of The IBOC Handbook, page 413


What is HD Radio? (FM)Also known as “IBOC”

The digital carriers merely transmit data: ones and zeros.

96kbps in standard mode 96kbps + 12 or 24kbps in extended hybrid modes Ext.Hybrid puts more digital carriers closer to the

analog signal – more risk for self-interference.

That digital payload can be divided in many ways, and not just for audio.


What is HD Radio? (AM)Also known as “IBOC” Also just transmits bits, but less bandwidth

– about 32kbps total.Multicasting is not available yet.Does have enough data (barely) for PAD.Chief advantage is in improved audio quality. Is authorized for operation at night and on

directional arrays.


What benefits does IBOC have? Robustness = no static, no fades, no multipath Quality = increases audio b/w from 15 to 20kHz

(i.e. more high end) for FM. Note, “quality” does not mean “fidelity” – it’s still a

lossy codec…but on FM it’s impressive. On AM, it’s more complicated, but generally better.

Flexibility = transmits DATA not AUDIO. You can, in theory, use those bits for lots of things. PAD, iTunes tagging, MP3 downloads, on-demand

text/audio/video.


FM IBOC’s Killer AppMulticasting = Extra Radio Stations on 1 Signal

HD1 must always be a simulcast of your analog signal. Multicasting changes 96kbps for HD signal into

subdivisions: 48kbps each : HD1 & HD2 32kbps each : HD1 & HD2 & HD3 48kbps : HD1 + 24kbps each : HD2 & HD3

Extended hybrid’s bits cannot be added to the 96kbps, but can be used alone for a single multicast channel. 48kbps each : HD1 & HD2 + 24kbps : HD3

Theoretical max up to HD7, practical limit is HD3 Less kbps = less audio quality HD4 is possible but problematic in many ways.


FM IBOC’s Killer App???iTunes Tagging

www.hdradio.com/iTunes_Tagging Equipped radios have a “tag” button.

Press when you hear a song you like. Radio saves tag info to your iPod. When iPod is connected to iTunes, it goes to iTunes

music store and buys the song for you. Very cool – but limited receivers, limited number

of stations doing it. Requires massive investment in audio content mgmt & promotions.


FM IBOC LimitationsThe -10 vs -20dB Debate : NPR Labs Study

IBOC injection is -20dB or 1/100th of analog ERP (1000w analog = 10w digital)

Coverage is considered inferior to analog Proposals to increase IBOC inj. to -10dB of

1/10th of analog ERP. Risk of severe adjacent channel interference.

Avg. 26% loss of analog coverage / 41% of stations receive interference to one-third of service population.

…but portable HD may not work without it.



Summer 2008 – NPR Labs released first comprehensive, accurate IBOC coverage prediction model.

At current -20dB IBOC ERP levels… Mobile coverage = equivalent of analog Indoor coverage = 50% of analog

At -10dB IBOC ERP levels… Mobile coverage = +18% over analog Indoor coverage = 88% of analog



Hi-Level Combined Xmitter Systems will require SIGNIFICANT extra capacity. Current HD xmitters de-rated by up to 50%

Take a 20kW analog ERP station… @ -20dB : ~23kW analog + ~2kW digital @ -10dB : ~23kW analog + ~21kW digital

…and ~21kW going into the reject load!!! Different for split-level combined, combined, or

separate systems – but you get the idea: it’s not just a case of adding more watts.


FM IBOC Challenges IBOC requires time-delay of analog to match the digital –

this can complicate your off-air monitoring scheme. Normal silence sensors may not work effectively.

Adding HD2 and HD3 is essentially like buying two new stations. It introduces significant challenges in programming, operations control, monitoring, etc.

Do you have trouble filling ONE station with programming 24/7? Imagine adding two more! Or two more studios!

Managing listener expectations – when the HD signal is lost, it just disappears immediately. That means HDn channels just mute (instead of fading out to static).


FM Translators and Boosters Boosters (Single Freq. Network)

NRSC-5 specs carrier synch, but no radios support it yet. Right now it’s only in prelim testing.

Relates to the -20 vs -10dB IBOC injection debate.

Translators require* a separate exporter license from iBiquity = big bucks for a small signal. * unless you get a heterodyning xlator, which are still

vaporware and are pricey ($10-$20k)


FMeXtra?

Digital SCA (Subcarrier) service Compatible with hybrid IBOC, but not all-

digital IBOC. Transmits 64 – 156kbps

Stereo, RDS, analog SCA = less kbps avail. Transmits DATA, but architecture only

supports audio via AAC at the moment.


FMeXtra

Not meant as a multicast service, but can be used that way.Really meant to supplant existing analog SCA

Only one model of radio currently available: tabletop “Aruba”. FM only.

Can function as a handy backup STL / TSL system (yourself or rent to others)AAC codec = quality audio @ low kbps


Shameless Self-PromotionThe IBOC Handbook : Understanding HD RadioTM Technology

Looking to really learn the engineering of IBOC / HD Radio? Read this book! First & Only Overview of the

Newly-Approved NRSC-5 (IBOC) Standard.

Authored by David Maxson Illustrated by Aaron Read

Available on Amazon.com


Final Thoughts

Questions – and please no: Rants, Screeds, Diatribes, Harangues, Raving, Tirades,

Bullyragging, Vociferation, Bloviating, Railing, Objurgating, Badgering, Molestation, Nettling, Ruffling, Badgering, Pestering, Heckling or Persecution.

Tell us your situation, we’ll opine if HD Radio or FMeXtra is right for you!

Aaron Read can be reached via www.friedbagels.com/blog Need an engineer? www.sbe.org

Date post:	15-Dec-2015
Category:	Documents
Upload:	isabelle-wrather
View:	213 times
Download:	0 times

No, your presenter is not “drinking the iBiquity Kool-Aid” IBOC / HD Radio TM : Engineering...

Documents