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Broadband Over Power Line
and Amateur Radio
Ed Hare, W1RFI
ARRL Laboratory Manager
225 Main St
Newington,CT [email protected]
860-594-0318
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Rules of W1RFI¶s Presentations
It is okay to get up and leave!
Everybody has to laugh at my jokes! I am the only one allowed to tell any jokes!
Ask questions any time.
Falling asleep. . .
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In the US, Regulated by FCC Part 15
On October 14, 2004 the FCC made significant
changes to the rules governing BPL
Although this was seen by some to mean thatthe FCC now allowed BPL, it had been legal all
along under existing FCC rules
The new rules place new restrictions on BPL
that are intended to control its interferencepotential
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The Thrill of Victory or the
Agony of Defeat?
When the FCC started out the BPL
Notice of Inquiry, Commissioner
Abernathy said that she believed that
most of the rules restricting BPL could
be changed.
The new rules did not remove a single
restriction, but added new ones
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What Was Kept? Absolute-maximum limits defined in Part 15
Carrier-current must meet limits for intentional
emitters Part 15 also is clear that unlicensed devices such as
BPL must not cause any harmful interference andthey must accept any interference caused to them
Manufacturer responsible for FCC authorizationand maximum limits
Operator responsible for harmful interference
Both components to the rules are necessary forPart 15 to work
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Intentional Emitter Radiated
Emissions Limits - HF
Sec 15.209 1.705-30.0 MHz -- 30 QV/m at 30 meters
These limits should protect users of the
spectrum against interference, yes?
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No! If the absolute emissions limits were set to offer
unconditional protection to all radio services, the
permitted levels would be unworkably low
Amateur Radio Service, by design, uses sensitiveequipment and weak signals
The ³legal limit´ will result in a strong signal to
nearby amateur HF installations On 3.5 MHz, a half-wave dipole placed in a 30 QV/m
field will receive a ±86.4 dBW signal (338 QV across50 ohms)
To amateurs, this is S9+16 dB ± clearly harmfulinterference to typical amateur communications!
The absolute limits are not enough to preventinterference to nearby receivers
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Levels: International work in progress:
FCC levels much higher than other nations or proposals
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The Bottom Line
The legal limits result in strong signals to
nearby receivers
Nearby receivers that will receive interferenceif they are trying to receive signals on the same
spectrum as analog signals
In residential neighborhoods, the risk is
typically to Amateur Radio, Citizens Band and
international shortwave broadcast
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Fields Near Large Radiators ± 14 MHz
30 meter/3 meter ratio 16 dB
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Harmful Interference
Defined as the repeated disruption of radio
communications or any disruption of certainemergency communications services
Merely hearing a signal is NOT harmfulinterference
30 QV/m at 30 m works to a degree for discretefrequency signals
If from broadband device, however, willinterfere with entire band(s)!
30 QV/m works to a degree for isolated pointsources
If from PLC, level will occur for entire lengthof line in areas where access PLC is deployed!
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Harmful Interference ± the BPL Perspective
"It is Progress Energy·s position and interpretation of theFCC's rules with regard to 'harmful interference' that any
interference that may still exist is not 'harmful' as that
term is defined by the FCC's rules," Len Anthony, PEC's
attorney for regulatory affairs, told James Burtle, chief of
the FCC's Experimental License Branch. "This level of interference does not seriously degrade ham radio
operation or transmissions or cause repeated
interruptions."
The FCC defines as "harmful" any interference that
"seriously degrades, obstructs or repeatedly interrupts a
radiocommunication service operating in accordance with
the Radio Regulations."
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How do I know it is BPL? It is possible to misidentify BPL
Each BPL system has a unique sound
Some are spread spectrum ± broadband noise
Some are OFDM, broadband noise or multiple
carrier Onset vs spectrum is generally over about 100
kHz
If the noise has a strong 60- or 120-Hz
component, it is probably ³regular´ power-linenoise
If heard every 10-50 kHz, as a buzz or asbirdies, it is probably a computer, TV set or
switch-mode power supply
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S pectrum Chart: This shows the present
use of spectrum:
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S pectrum with BPL from 2-80 MHz:
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BPL Could Interfere With: Emergency
management
National Guard
US Coast Guard
U.S. Military
Fire Departments Law Enforcement
CAP
FAA
FEMA
NASA
Voice of America
TV stations Amateur and CB
radio
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Other organizations that share
ARRL¶s concerns: Federal Emergency Management Agency
National short-wave listener associations
Short-wave broadcasters
Aeronautical
NTIA has done field measurements in
Potomac, MD and Emmaus, PA They released a report on their findings
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Examples from ARRL Filings
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Residential Noise + 10 dB
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Residential Noise Levels
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Part 15 Noise Levels
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EMC Issues
Proper test methods
Extrapolation vs height
Extrapolation vs distance Compatibility with radio services
Standards and good design practicemust take over where regulations
leave off
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Test methods Standards for test methods are under development
Measure at 1 meter height Below 30 MHz, extrapolate at 40 dB/decade ³slant-
range´
Above 30 MHz, extrapolate at 20 dB/decade
Above 30 MHz, add 5 dB for height Measure E field with magnetic loop
Other than measuring an electric field with amagnetic loop in the near field, what is wrong with
this test method? Actually, ARRL modeling showed good correlation
between E and H peaks
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Test Methods Measure in situ for 3 typical overhead and
underground wiring sites (6 sites)
Measure for CPE, injector, coupler, repeater
That¶s a lot of testing!
At 10 distances along line for 4 different devices of 5 MHz bandwidth between 5 and 50 MHz, that is:10 measurement points * 3 systems * 2 (overheadand underground) * 4 types of devices * 9frequency segments = 2160 scans
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Test Methods (continued)
G
ood practice requires that the 6 strongest peaksbe recorded and logged
And in situ, ambients will kill you, and each
³peak´ must be demodulated and a determination
made that it is a BPL signal, not an ambient
This is 2160 * 6 = 12,960 demodulations
G
oing from 10 meters horizontal to 3 metershorizontal doesn¶t buy much because the slant
range changes little
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Extrapolation vs Distance FCC rules speify that measurements made at other than
compliance distance may be extrapolated to compliancedistance
Rules specify 40 dB/distance decade below 30 MHz and 20dB/decade above 30 MHz
This is a wide range of opinion on whether 40 dB/decade isappropriate for line emitters
ARRL has provided FCC with antenna modeling andtheoretical analysis showing why a power line is a line source
Models show 40 dB/decade along ground
Models show 20 dB/decade for measurement made at 1meter to true maximum at height
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Example NEC Analysis
(Spatial Distribution of E Field)
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Ingress Initial tests show that BPL is susceptible to ingress
from nearby transmitters
Amateur radio may use EIRPs of 20 kW or more
Field strength at power lines may be 100 V/m (160dBuV/m), more typically 10 to 25 V/m
Tests show as little as 10 watts can take it down
More testing is needed, but industry reluctant to doso
Utilities reluctant, too, which is much lessunderstandable, although two are discussingimmunity testing with ARRL volunteers
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What is needed? It is critical that all unlicensed emitters that operate
anywhere near the FCC limits avoid locally used spectrum
To avoid degrading a licensed service, typically, a 1 dBdegradation is used
This would require that noise be 6 dB lower than the desiredsignal
If the median values of man-made noise are used for N, thenthe level of BPL emissions at the receive-system antenna onspectrum that must be protected would range from 0
dBuV/m on lower HF to ±10 dBuV/m on upper HF
This would generally protect mobile operation, and mostfixed operation
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What is needed?
The values of man-made noise in ITU P378-2are median values
Lower levels are common in communicationschannels used by services with frequencyagility
At some stations in the Amateur Radio Service,field strength at the antenna of ±20 dBuV/m inquiet areas of a given band would be found
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How can this be achieved?
Notching is a technique whereby BPL use of certain portions of spectrum is turned off
Notching is typically 20 to 30 dB notch depth
This is not enough to achieve the levels in the previous
slide if starting at the FCC limits. To achieve compatibility with nearby radio services,
operating at a lower emissions level and puttingadditional guard bands around spectrum that is being
protected is necessary
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How can this be achieved?
One way that the a lower operating level couldeasily be achieved with minimum changes to therules would be to use a smaller distanceextrapolation factor.
A formula that used about 30 dB/decade at 1 MHz,decreasing to 20 dB/decade above 30 MHz wouldmatch modeled and measured results
A simplification of this to 23 dB/decade would be areasonable approach
This would allow the typically achieved 25-30 dBnotching to be adequate to protect HF and low-VHF
mobile stations
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How can compatibility be
achieved? Some fixed stations require additional notch
depth
One BPL manufacturer has shown that it is practical to do this with hardware filters
These filters also help with ingress
They can be used in all of a product line, or be applied on a case by case basis whereneed, if they are available
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The goal is NOT to try to design systems
or regulations that have no potential for
interference. That would not be
reasonable or practical. An attainable goal
is to design systems that have a low-
enough incidence of interference that it is
practical to resolve that interference on a
case-by-case basis. This requires the
additional goals of having that practical
solution available and to use those
solutions where necessary.
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Is Amateur Radio Doomed?
No! In a speech last year, FCC Commissioner
Abernathy stated that she envisioned that mostrules that were restricting BPL could be removed.
In a letter issued several months later, she clarifiedthat protection against harmful interference was a³bedrock´ position.
In October, 2004, the FCC came out with an
announcement of new rules that removed NOrestrictions, but proposed to add requirements thatapply to no other unintentional emitter
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The work being done by amateur
radio IS having an effect, and wecan continue to emphasize to all
involved that power lines are not
the right place to put high-speed
digital signals using the same
spectrum as local radio receivers
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Video
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What is ARRL doing? Here¶s the short list«
Working with local amateurs in BPL areas Filing supporting interference complaints
Funding measurements in BPL areas where appropriate
Federal Court of Appeals if necessary
Maintaining contacts and presence in standards area Ed Hare is chair of IEEE EMCS SDCom BPL study
project
Making other affected users aware of BPL interferenceissues and explaining how to file complaints
Articles in QST and on ARRL web pages
Petition for Reconsideration
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Cooperation ARRL has a track record of working cooperatively with
industry Over years, it has worked with the cable industry;
VDSL; Home Phone Networking Alliance
It has worked with HomePlug on their Version 1
standard and expects to work with them on theupcoming AV standard
BPL industry generally believes cooperation meansdoing what they can, then when it falls short, start
³blaming the victim´ The door is still wide open for sincere cooperation
In one BPL test site, ³cooperation´ did not eveninclude the BPL manufacturer taking a 10-minute ride
to observe interference
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Recon Petition
Procedural and technical flaws in the rulemaking FCC concluded that interference potential low
650 pages of unreleased correspondence and testdata
This material showed unresolved interference anda considerable interference potential
FCC testing supported ARRL¶s position
Redaction
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EMC Standards Work
IEEE Standards Association 4 major standards under development
Hardware and safety (P1675) (PES)
EMC (P1775) (PES and EMCS)
Protocols and interoperability (P1902) (ComSoc)
By decision, EMC does not address compatibility with radioservices
IEEE EMC Society Standards Development CommitteeEMC Study Project
ANSI-accredited C63 BPL working group
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What Can You Do to Help?
Membership
File comments with FCC
Right place at the right time
SDCom BPL study project
Measurements
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Q&A
a.k.a. Stump the Speaker
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MORE INFORMATION
Ed Hare, W1RFI
ARRL Laboratory Manager
225 Main St
Newington,CT [email protected]
860-594-0318
http://www.arrl.org/bpl [email protected]
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