caused by interference from metal-to-metal noise in the linkage. The
other crashes that weekend were caused by “dumb-thumb”
maneuvers.
However, the damage was done. That field was labeled as having
a problem with BPL when BPL was nowhere nearby.
Loss of control is usually followed by placing blame on someone
or something beyond your influence. It’s human nature to say, “I
sure didn’t cause the crash; it must have been something else.” BPL
is the latest buzzword, and it is causing quite a stir. What is BPL?
Can it cause you problems?
Please take some time to read this. I know that technobabble can
glaze people’s eyes over faster than warm milk, but try to read on;
I’ll keep it to a minimum. It is important that everyone understand
the basics of what BPL is, what it is not, and what it can and cannot
do to us as modelers.
Broadband Over Power Lines, Access
BPL, or just plain BPL, is part of what is
generally known as power-line
communications. Utility companies have
used power-line communications for years,
to communicate telemetry between sites.
In BPL, Internet communication signals
are transmitted through the power lines and
are fed into the home. It is a high-speed
form of Internet service, much as cable
Internet service or Digital Subscriber Line
(DSL) phone-line Internet service.
At the head end of the line, the Internet
communication service connects to the
power lines using wireless to talk to a box
up on the utility pole. This box is called an
injector, and out of it come some highvoltage
clamps that “inject,” or magnetically
couple, the signals onto the power line. At
various points along the lines, the signal is
extracted, amplified, repeated through
wireless, and reinjected into the next section
of power lines.
by Dan Williams
Injector connected to pole and power line injects and removes
BPL signals from power lines. Photo courtesy ARRLWeb.
Does your model field have some of these structures (on the left) nearby? Rest assured
that BPL won’t be found anywhere near them. Photo courtesy the author.
JOHN JUST FINISHED his pride and joy: a Stand-Off Scale P-
51D Mustang. When he arrived at the field, he picked up the
frequency pin and his transmitter. Once the preflight checks were
completed, including a range check, John figured he was “good to
go.”
He was the only one on the flightline; all other transmitters were
in the impound. Everyone seemed captivated while watching the
maiden flight. After a bit of trimming during the first few passes, the
model was flying well. John let the dogs out and ripped a few rolls!
All was fine with the world.
With its gasoline engine sounding sweet, John decided to take
the P-51 up high and way out to set up for a big ol’ victory roll. He
rolled the model inverted and began a Split S. Suddenly there was a
twitch of the tail. Then another! In desperation, John yelled “I ain’t
got it!”
There was a sickening crunch as “Six Shooter” buried itself in
the ground way off the edge of the runway. “Somebody shot me
down!” John moaned. But as he looked around, he saw that
everyone was standing around the pits, nowhere near the impound.
All of the transmitters were there and were off. No one knew what to
say, but everyone headed out to the crash site to help with the
pickup.
“Something happened; I had no control at all,” John related.
“Ah, it must have been BPL,” said one of John’s buddies as they
walked. “I heard those systems are going in everywhere and they’re
causing crashes all over the country. That must’ve been what
happened.”
“Huh? I’ve heard of pagers and stuff, but not BPL,” said John.
“Maybe that was it.”
A couple more crashes during the long weekend served to
reinforce John’s friend’s proclamation. Little did John know that he
caused the crash by not range-checking with that big gasoline engine
running. He got the airplane far enough out, and the signal loss was
Low- to medium-level power lines, such as the ones shown,
may someday carry BPL signals. Photo courtesy ARRLWeb.
There are various manufacturers of BPL systems, and they do look
different. The big giveaway is large clamps that connect to topmost
lines on utility poles. Don’t confuse them with utility devices
such as transformers and capacitors that are part of the powerdistribution
system. Photo courtesy ARRLWeb.
This continues along the path in a huge network that becomes the
distribution means for Internet service. At the home, a special modem
extracts the signals from the power line and connects to your
computer.
The Federal Communications Commission (FCC) authorized the
testing of these BPL systems in a series of trials during the past few
years. The FCC and BPL manufacturers intentionally kept it quiet;
they did not want to arouse the suspicions of other users of the
frequencies they were utilizing.
Not until late in 2003—when the FCC put out a Notice of Inquiry
(NOI)—did it become evident that some changes were coming. The
NOI indicated that the FCC was going to incorporate the specifics of
BPL under FCC Part 15 rules. Part 15 regulates the output signal
power of unlicensed intentional and unintentional signal radiators,
such as computers and power supplies; somehow the FCC was going
to pigeonhole BPL into this rule.
AMA immediately took action through its attorney and responded
with a letter of objection, as did most others who used the radio bands
that could be affected.
FCC Part 15 was originally intended to regulate the emissions
from sources that are considered “point source radiators.” The
oscillators in your dual-conversion RC receivers, microwave ovens,
television sets, and garage-door openers are governed by this rule. All
of these devices have essentially one point where the emission
occurs.
On the other hand, BPL is a distributed source of radio-frequency
(RF) energy because the BPL signals are transmitted along
unshielded power lines. DSL is shielded with twisted telephone
wires. Cable service is protected with a braided shield. BPL is
transmitted along bare wires that were meant to transmit 60-hertz AC
(alternating current) power—not the many MHz of broadband RF
signals.
Although BPL was “technically” already allowable under FCC
Part 15, there were no specific rules and requirements. The BPL
manufacturers needed the specifics added to proceed with
deployment.
The potential problem with BPL is that the signals don’t stay
within the power line, as they do in cable broadband technology. The
power line radiates the signal like a big, old antenna. How far away
from the power line the signal is going to bother other services is a
source of contention and much debate among the users and the FCC.
BPL is authorized to operate on frequencies between 1.8 MHz and
80.0 MHz. This is above the AM (Amplitude Modulation) broadcast
band and below the FM (Frequency Modulation) broadcast band.
Meet Dan Williams
Dan Williams has been into aircraft modeling
since he was very young and has been active in RC
since 1979. He has been a licensed radio amateur
since 1977.
Dan graduated in 1980 from Clarkson College of
Technology (Potsdam NY) with a bachelor’s of
science degree in electrical engineering,
specializing in communication systems. He
obtained an FCC Commercial Radiotelephone
License in 1981 and has been involved in RCsystem
operation and repair since then.
In 1999 Dan became frequency coordinator for
AMA District II. In 2003 he was appointed to the
AMA Frequency Committee, where he has joined
the ongoing investigation into the impact of BPL
and new RC technologies on the future of RC
modeling. MA
Our airborne RC operations are in the 72
MHz band, near the upper end of the
allowable spectrum for BPL. The few
frequencies available on 27 MHz in the
Citizens’ Band (CB), some inexpensive
systems on 49 MHz, and licensed Handheld
Amateur Radio (HAM) operators who can
use the 50 MHz and 53 MHz frequencies for
RC are also affected.
Most RC modelers use our exclusive 50
frequencies in the 72 MHz band. Currently
the state-of-the-art BPL systems being
deployed in the test sites are operating
between 1.8 MHz and roughly 30.0 MHz—
well below our normally used RC band.
Early in 2004 the FCC put out a Notice
of Proposed Rulemaking (NPRM), which
meant that it was intending to move ahead
with BPL incorporation into FCC Part 15.
AMA, along with its attorney, drafted an
extensive letter outlining our objections to
the rulemaking.
The Amateur Radio Relay League
(ARRL—the HAM version of the AMA) has
done exhaustive impact studies on its
operations and included some serious
technical details in the report. We have been
in continual contact with the ARRL and its
engineering staff, and we have basically
aligned AMA with the ARRL to pool our
memberships on this issue.
As a result, the ARRL has provided us
with much more information about the tests
underway and the studies done. This has
been incredibly valuable in the effort to fight
BPL. This will also support our licensed
HAM operators who use the Six Meter band
for RC modeling.
In the NPRM, the FCC outlined a series
of tests that would be used to govern the
emissions from the BPL systems. At a given
distance and height away from the power
lines, the signal level would have to be
below the limit for FCC Part 15 emissions
from unlicensed equipment.
AMA is in the process of determining
whether or not those levels could be a
problem with our modeling operations. The
dilemma is that right now the BPL
equipment isn’t using the whole allotment of
frequencies. Testing our equipment for
compatibility with these systems has been
impossible.
We’ve attempted to do some tests on the
27 MHz band (CB) with equipment on the
few CB frequencies we have, but the results
have been inconclusive. Some BPL systems
have been “notching out,” or trying to limit
the amount of power used in the CB
frequencies. It has been difficult for AMA to
determine the effects.
October 28, 2004, the FCC released a
Rule and Order (RO). It made BPL official!
The order basically outlines everything that
was previously stated in the NPRM, with
several crucial and notable exceptions.
First, the equipment used for BPL must
be “certified” to meet FCC standards. This
was a big hit against the BPL manufacturers.
Now they must prove that the equipment
meets the standards rather than just verify it
or state that it does.
Second, the installer must verify the
equipment, indicating that it meets the Part
15 requirements. This means that the
equipment installer must ensure that it
doesn’t exceed the limits. All of the
providers must have test equipment available
to do the checking at the installation site.
This prevents installers from arbitrarily
“turning up” the power to make a particular
stubborn installation work.
I should point out that the BPL
manufacturers wanted a higher limit put in
place to make the system more reliable, but
the FCC didn’t give it to them.
Third, a public database must be kept of
all BPL installations, such that anyone can
determine exactly where a BPL system has
been deployed. Until now, the test sites have
been kept under tight wraps so that the BPL
opponents couldn’t easily scrutinize their
operation. The manufacturers and providers
really did not want this put into the ruling.
Those three points were advanced by the
Academy in its filings in an effort to exercise
some control over BPL operations. In
addition, BPL is only authorized to exist
through what is referred to as “license by
rule.” This is the same condition which
exists for our operations. Therefore, BPL is
required to cease operations if it interferes
with licensed operations.
These conditions serve to protect
everyone to a greater degree and actually
make BPL a “harder sell” when trying to
compete with cable or DSL.
What does all of this mean for us? The AMA
Frequency Committee viewed the small list of
test sites currently in operation. There has
been no widespread deployment of BPL to
date. There were only roughly a dozen
systems being tested, and they were limited in
size and scope. These sites were within
suburbs or small city areas, and not where the
average modelers would be flying their
airplanes.
BPL is only to be used in medium-voltage
lines, or the typical power lines that run down
the road in neighborhoods. It is not being used
in the high-voltage distribution lines. Many
model sites are within sight of some of these
towering “megavoltage” power lines; rest
assured that BPL will not be found here.
As of this writing, several of the dozen or
so systems that have been used for testing
have been shut down for various reasons.
Some companies have found that the return is
not worth the investment. Many studies show
that BPL is not the “cash cow” for providers
and utilities they thought it would be.
In some places, BPL just plain doesn’t
work well. Every several hundred feet, a new
repeater injector has to be installed on the
power lines to keep the signal going. This is a
cost issue. In many places, simple power-line
noise is causing grief for installers. They
cannot turn up the power to make things
work, so there are those places that can’t
receive BPL signals at all.
HAM-radio communicators have been
beating on the BPL providers in their areas.
HAM radio for communications has a real
problem in that the signals are weak by
nature, and they’re having a tough time
coping with the signal levels from BPL.
These communication signal levels are way
below the levels used for RC operations.
There has been such an outcry among the
HAM-radio community that some of the
providers find that the investment is not worth
the aggravation. This brings up another point
for us: signal levels.
Members of the AMA Frequency
Committee have been working with the
mathematics and system modeling studies to
see if these FCC Part 15 levels would really
be a problem for us. The jury is still out, but
initial indications are that the signals from our
transmitters are much stronger at quite some
distance from the receivers than the BPL
signals. Therefore, BPL may not be a concern
at all.
Theoretically, an RC receiver a half-mile
away from its transmitter and 30 feet from
power lines will have twice as much RC
signal as a BPL signal would produce. This
means that a model would have to be a halfmile
away and 60 feet or lower in altitude
directly above power lines containing BPL
signals for there to be any potential
interference.
It is doubtful that anyone would fly a
model that far away and that close to the
ground because of visual constraints,
especially near power lines. One can fly that
far away, but only if the model is at a higher
altitude.
Using the same figure of merit with
theoretical signal levels, a model that’s half of
that distance will have four times the RC
signal at the receiver. A quarter mile is a more
realistic distance for most sport-flying. Flying
at a 60-foot altitude a quarter-mile away is an
extreme case, so is there a problem?
Right now we don’t think so. A park flyer
may very well be flown within 60 feet of a
power line, but the transmitter is going to be
much closer to the receiver as well. There is
plenty of signal strength from the transmitter
for the receiver to lock onto.
This doesn’t take into account path losses.
Many assumptions are being made on both
sides of that issue. The modeling of a BPL
system radiation pattern is not trivial, and
there are numerous arguments taking place
about this.
There are conflicting results from studies
being done. One study indicates that after
approximately 100 feet from the power line,
the BPL signal level will be below the
background noise level. HAM-radio
communicators who have experienced BPL
interference firsthand beg to differ. However,
we have to be careful in comparing this to our
RC situation.
As time goes on, the BPL systems will
improve. They have to in order to overcome
the problems they have within their own
systems. They will have to improve their
systems just to compete against the other
modes of high-speed Internet service
already in existence. This will help serve the
other users of the bands too.
Late last summer I was involved in an
investigation of interference to RC
operations at a high-profile meet. Some
people at the event were certain that BPL
was the culprit, and that rumor spread on
the Internet like wildfire.
AMA set out with equipment in tow to
see what the problem was. We found an
extremely quiet 72 MHz RC band; we
didn’t find any BPL! According to our
attorney and other sources, BPL was not
being tested anywhere near this area, and
there was certainly nothing on our 72 MHz
band to indicate otherwise. We also found
a complete lack of any other meaningful
commercial activity.
Modelers are the primary users of 50
individual 72 MHz RC frequencies. They
are assigned by the FCC only for modelaircraft
operation. This assignment was the
direct result of AMA action taken in the
early 1980s.
However, the whole 72 MHz band does
not belong to us! We operate interstitially
with other users in between our
frequencies. Pager transmitters are the big
users and can be a source of trouble. I
bring this up because some will blame
BPL because of pager transmitters.
Is BPL a big problem for our future? It’s
going to be hard to prove false without
conclusive testing with BPL systems in
the 72 MHz band, but indications are that
it will not be a significant issue. The AMA
Frequency Committee is continuing the
investigation. It is certain that BPL will
continue to be the blame for
malfunctioning RC equipment, bad
installations, and dumb thumbs!
BPL deployment has been slowed by
the results of the testing and the
regulations that have been put in place.
Economics will also play a big role in the
slow pace of BPL as cable and DSL
Internet services continue to shore up their
position as established providers. Some
economic indicators are showing that BPL
is just not good business.
Would I hold off on buying RC
equipment on 72 MHz because of BPL?
Most certainly not. Each RC manufacturer
is making absolutely sure that its
equipment is the latest and greatest and
will prevent even the remote chance that
BPL could interfere. That’s good business
and good for RC.
Where do we go from here? The IEEE
(Institute of Electrical and Electronics
Engineers) has been tasked with coming
up with a set of standards for BPL
manufacturers and their operations. The
AMA Frequency Committee and the
ARRL have a vote on that committee to
protect licensed users. We’ve done all we
can legally with regard to filings as far as
the FCC is concerned, with one exception.
Once the RO is printed in the Federal
Registry, it is possible to file for
reconsideration. However, doing so would
require substantial proof that BPL poses a
significant threat. Such proof is
unavailable and is unlikely to be available
as long as BPL is operated strictly within
the FCC Part 15 rules.
Be assured that AMA will continue
working to protect our frequencies just as
it did when they were obtained for the RC
community! MA
Dan Williams
27 Treeline Dr.
Liverpool NY 13090
[email protected]
Edition: Model Aviation - 2005/04
Page Numbers: 73,74,76,78,80
Edition: Model Aviation - 2005/04
Page Numbers: 73,74,76,78,80
caused by interference from metal-to-metal noise in the linkage. The
other crashes that weekend were caused by “dumb-thumb”
maneuvers.
However, the damage was done. That field was labeled as having
a problem with BPL when BPL was nowhere nearby.
Loss of control is usually followed by placing blame on someone
or something beyond your influence. It’s human nature to say, “I
sure didn’t cause the crash; it must have been something else.” BPL
is the latest buzzword, and it is causing quite a stir. What is BPL?
Can it cause you problems?
Please take some time to read this. I know that technobabble can
glaze people’s eyes over faster than warm milk, but try to read on;
I’ll keep it to a minimum. It is important that everyone understand
the basics of what BPL is, what it is not, and what it can and cannot
do to us as modelers.
Broadband Over Power Lines, Access
BPL, or just plain BPL, is part of what is
generally known as power-line
communications. Utility companies have
used power-line communications for years,
to communicate telemetry between sites.
In BPL, Internet communication signals
are transmitted through the power lines and
are fed into the home. It is a high-speed
form of Internet service, much as cable
Internet service or Digital Subscriber Line
(DSL) phone-line Internet service.
At the head end of the line, the Internet
communication service connects to the
power lines using wireless to talk to a box
up on the utility pole. This box is called an
injector, and out of it come some highvoltage
clamps that “inject,” or magnetically
couple, the signals onto the power line. At
various points along the lines, the signal is
extracted, amplified, repeated through
wireless, and reinjected into the next section
of power lines.
by Dan Williams
Injector connected to pole and power line injects and removes
BPL signals from power lines. Photo courtesy ARRLWeb.
Does your model field have some of these structures (on the left) nearby? Rest assured
that BPL won’t be found anywhere near them. Photo courtesy the author.
JOHN JUST FINISHED his pride and joy: a Stand-Off Scale P-
51D Mustang. When he arrived at the field, he picked up the
frequency pin and his transmitter. Once the preflight checks were
completed, including a range check, John figured he was “good to
go.”
He was the only one on the flightline; all other transmitters were
in the impound. Everyone seemed captivated while watching the
maiden flight. After a bit of trimming during the first few passes, the
model was flying well. John let the dogs out and ripped a few rolls!
All was fine with the world.
With its gasoline engine sounding sweet, John decided to take
the P-51 up high and way out to set up for a big ol’ victory roll. He
rolled the model inverted and began a Split S. Suddenly there was a
twitch of the tail. Then another! In desperation, John yelled “I ain’t
got it!”
There was a sickening crunch as “Six Shooter” buried itself in
the ground way off the edge of the runway. “Somebody shot me
down!” John moaned. But as he looked around, he saw that
everyone was standing around the pits, nowhere near the impound.
All of the transmitters were there and were off. No one knew what to
say, but everyone headed out to the crash site to help with the
pickup.
“Something happened; I had no control at all,” John related.
“Ah, it must have been BPL,” said one of John’s buddies as they
walked. “I heard those systems are going in everywhere and they’re
causing crashes all over the country. That must’ve been what
happened.”
“Huh? I’ve heard of pagers and stuff, but not BPL,” said John.
“Maybe that was it.”
A couple more crashes during the long weekend served to
reinforce John’s friend’s proclamation. Little did John know that he
caused the crash by not range-checking with that big gasoline engine
running. He got the airplane far enough out, and the signal loss was
Low- to medium-level power lines, such as the ones shown,
may someday carry BPL signals. Photo courtesy ARRLWeb.
There are various manufacturers of BPL systems, and they do look
different. The big giveaway is large clamps that connect to topmost
lines on utility poles. Don’t confuse them with utility devices
such as transformers and capacitors that are part of the powerdistribution
system. Photo courtesy ARRLWeb.
This continues along the path in a huge network that becomes the
distribution means for Internet service. At the home, a special modem
extracts the signals from the power line and connects to your
computer.
The Federal Communications Commission (FCC) authorized the
testing of these BPL systems in a series of trials during the past few
years. The FCC and BPL manufacturers intentionally kept it quiet;
they did not want to arouse the suspicions of other users of the
frequencies they were utilizing.
Not until late in 2003—when the FCC put out a Notice of Inquiry
(NOI)—did it become evident that some changes were coming. The
NOI indicated that the FCC was going to incorporate the specifics of
BPL under FCC Part 15 rules. Part 15 regulates the output signal
power of unlicensed intentional and unintentional signal radiators,
such as computers and power supplies; somehow the FCC was going
to pigeonhole BPL into this rule.
AMA immediately took action through its attorney and responded
with a letter of objection, as did most others who used the radio bands
that could be affected.
FCC Part 15 was originally intended to regulate the emissions
from sources that are considered “point source radiators.” The
oscillators in your dual-conversion RC receivers, microwave ovens,
television sets, and garage-door openers are governed by this rule. All
of these devices have essentially one point where the emission
occurs.
On the other hand, BPL is a distributed source of radio-frequency
(RF) energy because the BPL signals are transmitted along
unshielded power lines. DSL is shielded with twisted telephone
wires. Cable service is protected with a braided shield. BPL is
transmitted along bare wires that were meant to transmit 60-hertz AC
(alternating current) power—not the many MHz of broadband RF
signals.
Although BPL was “technically” already allowable under FCC
Part 15, there were no specific rules and requirements. The BPL
manufacturers needed the specifics added to proceed with
deployment.
The potential problem with BPL is that the signals don’t stay
within the power line, as they do in cable broadband technology. The
power line radiates the signal like a big, old antenna. How far away
from the power line the signal is going to bother other services is a
source of contention and much debate among the users and the FCC.
BPL is authorized to operate on frequencies between 1.8 MHz and
80.0 MHz. This is above the AM (Amplitude Modulation) broadcast
band and below the FM (Frequency Modulation) broadcast band.
Meet Dan Williams
Dan Williams has been into aircraft modeling
since he was very young and has been active in RC
since 1979. He has been a licensed radio amateur
since 1977.
Dan graduated in 1980 from Clarkson College of
Technology (Potsdam NY) with a bachelor’s of
science degree in electrical engineering,
specializing in communication systems. He
obtained an FCC Commercial Radiotelephone
License in 1981 and has been involved in RCsystem
operation and repair since then.
In 1999 Dan became frequency coordinator for
AMA District II. In 2003 he was appointed to the
AMA Frequency Committee, where he has joined
the ongoing investigation into the impact of BPL
and new RC technologies on the future of RC
modeling. MA
Our airborne RC operations are in the 72
MHz band, near the upper end of the
allowable spectrum for BPL. The few
frequencies available on 27 MHz in the
Citizens’ Band (CB), some inexpensive
systems on 49 MHz, and licensed Handheld
Amateur Radio (HAM) operators who can
use the 50 MHz and 53 MHz frequencies for
RC are also affected.
Most RC modelers use our exclusive 50
frequencies in the 72 MHz band. Currently
the state-of-the-art BPL systems being
deployed in the test sites are operating
between 1.8 MHz and roughly 30.0 MHz—
well below our normally used RC band.
Early in 2004 the FCC put out a Notice
of Proposed Rulemaking (NPRM), which
meant that it was intending to move ahead
with BPL incorporation into FCC Part 15.
AMA, along with its attorney, drafted an
extensive letter outlining our objections to
the rulemaking.
The Amateur Radio Relay League
(ARRL—the HAM version of the AMA) has
done exhaustive impact studies on its
operations and included some serious
technical details in the report. We have been
in continual contact with the ARRL and its
engineering staff, and we have basically
aligned AMA with the ARRL to pool our
memberships on this issue.
As a result, the ARRL has provided us
with much more information about the tests
underway and the studies done. This has
been incredibly valuable in the effort to fight
BPL. This will also support our licensed
HAM operators who use the Six Meter band
for RC modeling.
In the NPRM, the FCC outlined a series
of tests that would be used to govern the
emissions from the BPL systems. At a given
distance and height away from the power
lines, the signal level would have to be
below the limit for FCC Part 15 emissions
from unlicensed equipment.
AMA is in the process of determining
whether or not those levels could be a
problem with our modeling operations. The
dilemma is that right now the BPL
equipment isn’t using the whole allotment of
frequencies. Testing our equipment for
compatibility with these systems has been
impossible.
We’ve attempted to do some tests on the
27 MHz band (CB) with equipment on the
few CB frequencies we have, but the results
have been inconclusive. Some BPL systems
have been “notching out,” or trying to limit
the amount of power used in the CB
frequencies. It has been difficult for AMA to
determine the effects.
October 28, 2004, the FCC released a
Rule and Order (RO). It made BPL official!
The order basically outlines everything that
was previously stated in the NPRM, with
several crucial and notable exceptions.
First, the equipment used for BPL must
be “certified” to meet FCC standards. This
was a big hit against the BPL manufacturers.
Now they must prove that the equipment
meets the standards rather than just verify it
or state that it does.
Second, the installer must verify the
equipment, indicating that it meets the Part
15 requirements. This means that the
equipment installer must ensure that it
doesn’t exceed the limits. All of the
providers must have test equipment available
to do the checking at the installation site.
This prevents installers from arbitrarily
“turning up” the power to make a particular
stubborn installation work.
I should point out that the BPL
manufacturers wanted a higher limit put in
place to make the system more reliable, but
the FCC didn’t give it to them.
Third, a public database must be kept of
all BPL installations, such that anyone can
determine exactly where a BPL system has
been deployed. Until now, the test sites have
been kept under tight wraps so that the BPL
opponents couldn’t easily scrutinize their
operation. The manufacturers and providers
really did not want this put into the ruling.
Those three points were advanced by the
Academy in its filings in an effort to exercise
some control over BPL operations. In
addition, BPL is only authorized to exist
through what is referred to as “license by
rule.” This is the same condition which
exists for our operations. Therefore, BPL is
required to cease operations if it interferes
with licensed operations.
These conditions serve to protect
everyone to a greater degree and actually
make BPL a “harder sell” when trying to
compete with cable or DSL.
What does all of this mean for us? The AMA
Frequency Committee viewed the small list of
test sites currently in operation. There has
been no widespread deployment of BPL to
date. There were only roughly a dozen
systems being tested, and they were limited in
size and scope. These sites were within
suburbs or small city areas, and not where the
average modelers would be flying their
airplanes.
BPL is only to be used in medium-voltage
lines, or the typical power lines that run down
the road in neighborhoods. It is not being used
in the high-voltage distribution lines. Many
model sites are within sight of some of these
towering “megavoltage” power lines; rest
assured that BPL will not be found here.
As of this writing, several of the dozen or
so systems that have been used for testing
have been shut down for various reasons.
Some companies have found that the return is
not worth the investment. Many studies show
that BPL is not the “cash cow” for providers
and utilities they thought it would be.
In some places, BPL just plain doesn’t
work well. Every several hundred feet, a new
repeater injector has to be installed on the
power lines to keep the signal going. This is a
cost issue. In many places, simple power-line
noise is causing grief for installers. They
cannot turn up the power to make things
work, so there are those places that can’t
receive BPL signals at all.
HAM-radio communicators have been
beating on the BPL providers in their areas.
HAM radio for communications has a real
problem in that the signals are weak by
nature, and they’re having a tough time
coping with the signal levels from BPL.
These communication signal levels are way
below the levels used for RC operations.
There has been such an outcry among the
HAM-radio community that some of the
providers find that the investment is not worth
the aggravation. This brings up another point
for us: signal levels.
Members of the AMA Frequency
Committee have been working with the
mathematics and system modeling studies to
see if these FCC Part 15 levels would really
be a problem for us. The jury is still out, but
initial indications are that the signals from our
transmitters are much stronger at quite some
distance from the receivers than the BPL
signals. Therefore, BPL may not be a concern
at all.
Theoretically, an RC receiver a half-mile
away from its transmitter and 30 feet from
power lines will have twice as much RC
signal as a BPL signal would produce. This
means that a model would have to be a halfmile
away and 60 feet or lower in altitude
directly above power lines containing BPL
signals for there to be any potential
interference.
It is doubtful that anyone would fly a
model that far away and that close to the
ground because of visual constraints,
especially near power lines. One can fly that
far away, but only if the model is at a higher
altitude.
Using the same figure of merit with
theoretical signal levels, a model that’s half of
that distance will have four times the RC
signal at the receiver. A quarter mile is a more
realistic distance for most sport-flying. Flying
at a 60-foot altitude a quarter-mile away is an
extreme case, so is there a problem?
Right now we don’t think so. A park flyer
may very well be flown within 60 feet of a
power line, but the transmitter is going to be
much closer to the receiver as well. There is
plenty of signal strength from the transmitter
for the receiver to lock onto.
This doesn’t take into account path losses.
Many assumptions are being made on both
sides of that issue. The modeling of a BPL
system radiation pattern is not trivial, and
there are numerous arguments taking place
about this.
There are conflicting results from studies
being done. One study indicates that after
approximately 100 feet from the power line,
the BPL signal level will be below the
background noise level. HAM-radio
communicators who have experienced BPL
interference firsthand beg to differ. However,
we have to be careful in comparing this to our
RC situation.
As time goes on, the BPL systems will
improve. They have to in order to overcome
the problems they have within their own
systems. They will have to improve their
systems just to compete against the other
modes of high-speed Internet service
already in existence. This will help serve the
other users of the bands too.
Late last summer I was involved in an
investigation of interference to RC
operations at a high-profile meet. Some
people at the event were certain that BPL
was the culprit, and that rumor spread on
the Internet like wildfire.
AMA set out with equipment in tow to
see what the problem was. We found an
extremely quiet 72 MHz RC band; we
didn’t find any BPL! According to our
attorney and other sources, BPL was not
being tested anywhere near this area, and
there was certainly nothing on our 72 MHz
band to indicate otherwise. We also found
a complete lack of any other meaningful
commercial activity.
Modelers are the primary users of 50
individual 72 MHz RC frequencies. They
are assigned by the FCC only for modelaircraft
operation. This assignment was the
direct result of AMA action taken in the
early 1980s.
However, the whole 72 MHz band does
not belong to us! We operate interstitially
with other users in between our
frequencies. Pager transmitters are the big
users and can be a source of trouble. I
bring this up because some will blame
BPL because of pager transmitters.
Is BPL a big problem for our future? It’s
going to be hard to prove false without
conclusive testing with BPL systems in
the 72 MHz band, but indications are that
it will not be a significant issue. The AMA
Frequency Committee is continuing the
investigation. It is certain that BPL will
continue to be the blame for
malfunctioning RC equipment, bad
installations, and dumb thumbs!
BPL deployment has been slowed by
the results of the testing and the
regulations that have been put in place.
Economics will also play a big role in the
slow pace of BPL as cable and DSL
Internet services continue to shore up their
position as established providers. Some
economic indicators are showing that BPL
is just not good business.
Would I hold off on buying RC
equipment on 72 MHz because of BPL?
Most certainly not. Each RC manufacturer
is making absolutely sure that its
equipment is the latest and greatest and
will prevent even the remote chance that
BPL could interfere. That’s good business
and good for RC.
Where do we go from here? The IEEE
(Institute of Electrical and Electronics
Engineers) has been tasked with coming
up with a set of standards for BPL
manufacturers and their operations. The
AMA Frequency Committee and the
ARRL have a vote on that committee to
protect licensed users. We’ve done all we
can legally with regard to filings as far as
the FCC is concerned, with one exception.
Once the RO is printed in the Federal
Registry, it is possible to file for
reconsideration. However, doing so would
require substantial proof that BPL poses a
significant threat. Such proof is
unavailable and is unlikely to be available
as long as BPL is operated strictly within
the FCC Part 15 rules.
Be assured that AMA will continue
working to protect our frequencies just as
it did when they were obtained for the RC
community! MA
Dan Williams
27 Treeline Dr.
Liverpool NY 13090
[email protected]
Edition: Model Aviation - 2005/04
Page Numbers: 73,74,76,78,80
caused by interference from metal-to-metal noise in the linkage. The
other crashes that weekend were caused by “dumb-thumb”
maneuvers.
However, the damage was done. That field was labeled as having
a problem with BPL when BPL was nowhere nearby.
Loss of control is usually followed by placing blame on someone
or something beyond your influence. It’s human nature to say, “I
sure didn’t cause the crash; it must have been something else.” BPL
is the latest buzzword, and it is causing quite a stir. What is BPL?
Can it cause you problems?
Please take some time to read this. I know that technobabble can
glaze people’s eyes over faster than warm milk, but try to read on;
I’ll keep it to a minimum. It is important that everyone understand
the basics of what BPL is, what it is not, and what it can and cannot
do to us as modelers.
Broadband Over Power Lines, Access
BPL, or just plain BPL, is part of what is
generally known as power-line
communications. Utility companies have
used power-line communications for years,
to communicate telemetry between sites.
In BPL, Internet communication signals
are transmitted through the power lines and
are fed into the home. It is a high-speed
form of Internet service, much as cable
Internet service or Digital Subscriber Line
(DSL) phone-line Internet service.
At the head end of the line, the Internet
communication service connects to the
power lines using wireless to talk to a box
up on the utility pole. This box is called an
injector, and out of it come some highvoltage
clamps that “inject,” or magnetically
couple, the signals onto the power line. At
various points along the lines, the signal is
extracted, amplified, repeated through
wireless, and reinjected into the next section
of power lines.
by Dan Williams
Injector connected to pole and power line injects and removes
BPL signals from power lines. Photo courtesy ARRLWeb.
Does your model field have some of these structures (on the left) nearby? Rest assured
that BPL won’t be found anywhere near them. Photo courtesy the author.
JOHN JUST FINISHED his pride and joy: a Stand-Off Scale P-
51D Mustang. When he arrived at the field, he picked up the
frequency pin and his transmitter. Once the preflight checks were
completed, including a range check, John figured he was “good to
go.”
He was the only one on the flightline; all other transmitters were
in the impound. Everyone seemed captivated while watching the
maiden flight. After a bit of trimming during the first few passes, the
model was flying well. John let the dogs out and ripped a few rolls!
All was fine with the world.
With its gasoline engine sounding sweet, John decided to take
the P-51 up high and way out to set up for a big ol’ victory roll. He
rolled the model inverted and began a Split S. Suddenly there was a
twitch of the tail. Then another! In desperation, John yelled “I ain’t
got it!”
There was a sickening crunch as “Six Shooter” buried itself in
the ground way off the edge of the runway. “Somebody shot me
down!” John moaned. But as he looked around, he saw that
everyone was standing around the pits, nowhere near the impound.
All of the transmitters were there and were off. No one knew what to
say, but everyone headed out to the crash site to help with the
pickup.
“Something happened; I had no control at all,” John related.
“Ah, it must have been BPL,” said one of John’s buddies as they
walked. “I heard those systems are going in everywhere and they’re
causing crashes all over the country. That must’ve been what
happened.”
“Huh? I’ve heard of pagers and stuff, but not BPL,” said John.
“Maybe that was it.”
A couple more crashes during the long weekend served to
reinforce John’s friend’s proclamation. Little did John know that he
caused the crash by not range-checking with that big gasoline engine
running. He got the airplane far enough out, and the signal loss was
Low- to medium-level power lines, such as the ones shown,
may someday carry BPL signals. Photo courtesy ARRLWeb.
There are various manufacturers of BPL systems, and they do look
different. The big giveaway is large clamps that connect to topmost
lines on utility poles. Don’t confuse them with utility devices
such as transformers and capacitors that are part of the powerdistribution
system. Photo courtesy ARRLWeb.
This continues along the path in a huge network that becomes the
distribution means for Internet service. At the home, a special modem
extracts the signals from the power line and connects to your
computer.
The Federal Communications Commission (FCC) authorized the
testing of these BPL systems in a series of trials during the past few
years. The FCC and BPL manufacturers intentionally kept it quiet;
they did not want to arouse the suspicions of other users of the
frequencies they were utilizing.
Not until late in 2003—when the FCC put out a Notice of Inquiry
(NOI)—did it become evident that some changes were coming. The
NOI indicated that the FCC was going to incorporate the specifics of
BPL under FCC Part 15 rules. Part 15 regulates the output signal
power of unlicensed intentional and unintentional signal radiators,
such as computers and power supplies; somehow the FCC was going
to pigeonhole BPL into this rule.
AMA immediately took action through its attorney and responded
with a letter of objection, as did most others who used the radio bands
that could be affected.
FCC Part 15 was originally intended to regulate the emissions
from sources that are considered “point source radiators.” The
oscillators in your dual-conversion RC receivers, microwave ovens,
television sets, and garage-door openers are governed by this rule. All
of these devices have essentially one point where the emission
occurs.
On the other hand, BPL is a distributed source of radio-frequency
(RF) energy because the BPL signals are transmitted along
unshielded power lines. DSL is shielded with twisted telephone
wires. Cable service is protected with a braided shield. BPL is
transmitted along bare wires that were meant to transmit 60-hertz AC
(alternating current) power—not the many MHz of broadband RF
signals.
Although BPL was “technically” already allowable under FCC
Part 15, there were no specific rules and requirements. The BPL
manufacturers needed the specifics added to proceed with
deployment.
The potential problem with BPL is that the signals don’t stay
within the power line, as they do in cable broadband technology. The
power line radiates the signal like a big, old antenna. How far away
from the power line the signal is going to bother other services is a
source of contention and much debate among the users and the FCC.
BPL is authorized to operate on frequencies between 1.8 MHz and
80.0 MHz. This is above the AM (Amplitude Modulation) broadcast
band and below the FM (Frequency Modulation) broadcast band.
Meet Dan Williams
Dan Williams has been into aircraft modeling
since he was very young and has been active in RC
since 1979. He has been a licensed radio amateur
since 1977.
Dan graduated in 1980 from Clarkson College of
Technology (Potsdam NY) with a bachelor’s of
science degree in electrical engineering,
specializing in communication systems. He
obtained an FCC Commercial Radiotelephone
License in 1981 and has been involved in RCsystem
operation and repair since then.
In 1999 Dan became frequency coordinator for
AMA District II. In 2003 he was appointed to the
AMA Frequency Committee, where he has joined
the ongoing investigation into the impact of BPL
and new RC technologies on the future of RC
modeling. MA
Our airborne RC operations are in the 72
MHz band, near the upper end of the
allowable spectrum for BPL. The few
frequencies available on 27 MHz in the
Citizens’ Band (CB), some inexpensive
systems on 49 MHz, and licensed Handheld
Amateur Radio (HAM) operators who can
use the 50 MHz and 53 MHz frequencies for
RC are also affected.
Most RC modelers use our exclusive 50
frequencies in the 72 MHz band. Currently
the state-of-the-art BPL systems being
deployed in the test sites are operating
between 1.8 MHz and roughly 30.0 MHz—
well below our normally used RC band.
Early in 2004 the FCC put out a Notice
of Proposed Rulemaking (NPRM), which
meant that it was intending to move ahead
with BPL incorporation into FCC Part 15.
AMA, along with its attorney, drafted an
extensive letter outlining our objections to
the rulemaking.
The Amateur Radio Relay League
(ARRL—the HAM version of the AMA) has
done exhaustive impact studies on its
operations and included some serious
technical details in the report. We have been
in continual contact with the ARRL and its
engineering staff, and we have basically
aligned AMA with the ARRL to pool our
memberships on this issue.
As a result, the ARRL has provided us
with much more information about the tests
underway and the studies done. This has
been incredibly valuable in the effort to fight
BPL. This will also support our licensed
HAM operators who use the Six Meter band
for RC modeling.
In the NPRM, the FCC outlined a series
of tests that would be used to govern the
emissions from the BPL systems. At a given
distance and height away from the power
lines, the signal level would have to be
below the limit for FCC Part 15 emissions
from unlicensed equipment.
AMA is in the process of determining
whether or not those levels could be a
problem with our modeling operations. The
dilemma is that right now the BPL
equipment isn’t using the whole allotment of
frequencies. Testing our equipment for
compatibility with these systems has been
impossible.
We’ve attempted to do some tests on the
27 MHz band (CB) with equipment on the
few CB frequencies we have, but the results
have been inconclusive. Some BPL systems
have been “notching out,” or trying to limit
the amount of power used in the CB
frequencies. It has been difficult for AMA to
determine the effects.
October 28, 2004, the FCC released a
Rule and Order (RO). It made BPL official!
The order basically outlines everything that
was previously stated in the NPRM, with
several crucial and notable exceptions.
First, the equipment used for BPL must
be “certified” to meet FCC standards. This
was a big hit against the BPL manufacturers.
Now they must prove that the equipment
meets the standards rather than just verify it
or state that it does.
Second, the installer must verify the
equipment, indicating that it meets the Part
15 requirements. This means that the
equipment installer must ensure that it
doesn’t exceed the limits. All of the
providers must have test equipment available
to do the checking at the installation site.
This prevents installers from arbitrarily
“turning up” the power to make a particular
stubborn installation work.
I should point out that the BPL
manufacturers wanted a higher limit put in
place to make the system more reliable, but
the FCC didn’t give it to them.
Third, a public database must be kept of
all BPL installations, such that anyone can
determine exactly where a BPL system has
been deployed. Until now, the test sites have
been kept under tight wraps so that the BPL
opponents couldn’t easily scrutinize their
operation. The manufacturers and providers
really did not want this put into the ruling.
Those three points were advanced by the
Academy in its filings in an effort to exercise
some control over BPL operations. In
addition, BPL is only authorized to exist
through what is referred to as “license by
rule.” This is the same condition which
exists for our operations. Therefore, BPL is
required to cease operations if it interferes
with licensed operations.
These conditions serve to protect
everyone to a greater degree and actually
make BPL a “harder sell” when trying to
compete with cable or DSL.
What does all of this mean for us? The AMA
Frequency Committee viewed the small list of
test sites currently in operation. There has
been no widespread deployment of BPL to
date. There were only roughly a dozen
systems being tested, and they were limited in
size and scope. These sites were within
suburbs or small city areas, and not where the
average modelers would be flying their
airplanes.
BPL is only to be used in medium-voltage
lines, or the typical power lines that run down
the road in neighborhoods. It is not being used
in the high-voltage distribution lines. Many
model sites are within sight of some of these
towering “megavoltage” power lines; rest
assured that BPL will not be found here.
As of this writing, several of the dozen or
so systems that have been used for testing
have been shut down for various reasons.
Some companies have found that the return is
not worth the investment. Many studies show
that BPL is not the “cash cow” for providers
and utilities they thought it would be.
In some places, BPL just plain doesn’t
work well. Every several hundred feet, a new
repeater injector has to be installed on the
power lines to keep the signal going. This is a
cost issue. In many places, simple power-line
noise is causing grief for installers. They
cannot turn up the power to make things
work, so there are those places that can’t
receive BPL signals at all.
HAM-radio communicators have been
beating on the BPL providers in their areas.
HAM radio for communications has a real
problem in that the signals are weak by
nature, and they’re having a tough time
coping with the signal levels from BPL.
These communication signal levels are way
below the levels used for RC operations.
There has been such an outcry among the
HAM-radio community that some of the
providers find that the investment is not worth
the aggravation. This brings up another point
for us: signal levels.
Members of the AMA Frequency
Committee have been working with the
mathematics and system modeling studies to
see if these FCC Part 15 levels would really
be a problem for us. The jury is still out, but
initial indications are that the signals from our
transmitters are much stronger at quite some
distance from the receivers than the BPL
signals. Therefore, BPL may not be a concern
at all.
Theoretically, an RC receiver a half-mile
away from its transmitter and 30 feet from
power lines will have twice as much RC
signal as a BPL signal would produce. This
means that a model would have to be a halfmile
away and 60 feet or lower in altitude
directly above power lines containing BPL
signals for there to be any potential
interference.
It is doubtful that anyone would fly a
model that far away and that close to the
ground because of visual constraints,
especially near power lines. One can fly that
far away, but only if the model is at a higher
altitude.
Using the same figure of merit with
theoretical signal levels, a model that’s half of
that distance will have four times the RC
signal at the receiver. A quarter mile is a more
realistic distance for most sport-flying. Flying
at a 60-foot altitude a quarter-mile away is an
extreme case, so is there a problem?
Right now we don’t think so. A park flyer
may very well be flown within 60 feet of a
power line, but the transmitter is going to be
much closer to the receiver as well. There is
plenty of signal strength from the transmitter
for the receiver to lock onto.
This doesn’t take into account path losses.
Many assumptions are being made on both
sides of that issue. The modeling of a BPL
system radiation pattern is not trivial, and
there are numerous arguments taking place
about this.
There are conflicting results from studies
being done. One study indicates that after
approximately 100 feet from the power line,
the BPL signal level will be below the
background noise level. HAM-radio
communicators who have experienced BPL
interference firsthand beg to differ. However,
we have to be careful in comparing this to our
RC situation.
As time goes on, the BPL systems will
improve. They have to in order to overcome
the problems they have within their own
systems. They will have to improve their
systems just to compete against the other
modes of high-speed Internet service
already in existence. This will help serve the
other users of the bands too.
Late last summer I was involved in an
investigation of interference to RC
operations at a high-profile meet. Some
people at the event were certain that BPL
was the culprit, and that rumor spread on
the Internet like wildfire.
AMA set out with equipment in tow to
see what the problem was. We found an
extremely quiet 72 MHz RC band; we
didn’t find any BPL! According to our
attorney and other sources, BPL was not
being tested anywhere near this area, and
there was certainly nothing on our 72 MHz
band to indicate otherwise. We also found
a complete lack of any other meaningful
commercial activity.
Modelers are the primary users of 50
individual 72 MHz RC frequencies. They
are assigned by the FCC only for modelaircraft
operation. This assignment was the
direct result of AMA action taken in the
early 1980s.
However, the whole 72 MHz band does
not belong to us! We operate interstitially
with other users in between our
frequencies. Pager transmitters are the big
users and can be a source of trouble. I
bring this up because some will blame
BPL because of pager transmitters.
Is BPL a big problem for our future? It’s
going to be hard to prove false without
conclusive testing with BPL systems in
the 72 MHz band, but indications are that
it will not be a significant issue. The AMA
Frequency Committee is continuing the
investigation. It is certain that BPL will
continue to be the blame for
malfunctioning RC equipment, bad
installations, and dumb thumbs!
BPL deployment has been slowed by
the results of the testing and the
regulations that have been put in place.
Economics will also play a big role in the
slow pace of BPL as cable and DSL
Internet services continue to shore up their
position as established providers. Some
economic indicators are showing that BPL
is just not good business.
Would I hold off on buying RC
equipment on 72 MHz because of BPL?
Most certainly not. Each RC manufacturer
is making absolutely sure that its
equipment is the latest and greatest and
will prevent even the remote chance that
BPL could interfere. That’s good business
and good for RC.
Where do we go from here? The IEEE
(Institute of Electrical and Electronics
Engineers) has been tasked with coming
up with a set of standards for BPL
manufacturers and their operations. The
AMA Frequency Committee and the
ARRL have a vote on that committee to
protect licensed users. We’ve done all we
can legally with regard to filings as far as
the FCC is concerned, with one exception.
Once the RO is printed in the Federal
Registry, it is possible to file for
reconsideration. However, doing so would
require substantial proof that BPL poses a
significant threat. Such proof is
unavailable and is unlikely to be available
as long as BPL is operated strictly within
the FCC Part 15 rules.
Be assured that AMA will continue
working to protect our frequencies just as
it did when they were obtained for the RC
community! MA
Dan Williams
27 Treeline Dr.
Liverpool NY 13090
[email protected]
Edition: Model Aviation - 2005/04
Page Numbers: 73,74,76,78,80
caused by interference from metal-to-metal noise in the linkage. The
other crashes that weekend were caused by “dumb-thumb”
maneuvers.
However, the damage was done. That field was labeled as having
a problem with BPL when BPL was nowhere nearby.
Loss of control is usually followed by placing blame on someone
or something beyond your influence. It’s human nature to say, “I
sure didn’t cause the crash; it must have been something else.” BPL
is the latest buzzword, and it is causing quite a stir. What is BPL?
Can it cause you problems?
Please take some time to read this. I know that technobabble can
glaze people’s eyes over faster than warm milk, but try to read on;
I’ll keep it to a minimum. It is important that everyone understand
the basics of what BPL is, what it is not, and what it can and cannot
do to us as modelers.
Broadband Over Power Lines, Access
BPL, or just plain BPL, is part of what is
generally known as power-line
communications. Utility companies have
used power-line communications for years,
to communicate telemetry between sites.
In BPL, Internet communication signals
are transmitted through the power lines and
are fed into the home. It is a high-speed
form of Internet service, much as cable
Internet service or Digital Subscriber Line
(DSL) phone-line Internet service.
At the head end of the line, the Internet
communication service connects to the
power lines using wireless to talk to a box
up on the utility pole. This box is called an
injector, and out of it come some highvoltage
clamps that “inject,” or magnetically
couple, the signals onto the power line. At
various points along the lines, the signal is
extracted, amplified, repeated through
wireless, and reinjected into the next section
of power lines.
by Dan Williams
Injector connected to pole and power line injects and removes
BPL signals from power lines. Photo courtesy ARRLWeb.
Does your model field have some of these structures (on the left) nearby? Rest assured
that BPL won’t be found anywhere near them. Photo courtesy the author.
JOHN JUST FINISHED his pride and joy: a Stand-Off Scale P-
51D Mustang. When he arrived at the field, he picked up the
frequency pin and his transmitter. Once the preflight checks were
completed, including a range check, John figured he was “good to
go.”
He was the only one on the flightline; all other transmitters were
in the impound. Everyone seemed captivated while watching the
maiden flight. After a bit of trimming during the first few passes, the
model was flying well. John let the dogs out and ripped a few rolls!
All was fine with the world.
With its gasoline engine sounding sweet, John decided to take
the P-51 up high and way out to set up for a big ol’ victory roll. He
rolled the model inverted and began a Split S. Suddenly there was a
twitch of the tail. Then another! In desperation, John yelled “I ain’t
got it!”
There was a sickening crunch as “Six Shooter” buried itself in
the ground way off the edge of the runway. “Somebody shot me
down!” John moaned. But as he looked around, he saw that
everyone was standing around the pits, nowhere near the impound.
All of the transmitters were there and were off. No one knew what to
say, but everyone headed out to the crash site to help with the
pickup.
“Something happened; I had no control at all,” John related.
“Ah, it must have been BPL,” said one of John’s buddies as they
walked. “I heard those systems are going in everywhere and they’re
causing crashes all over the country. That must’ve been what
happened.”
“Huh? I’ve heard of pagers and stuff, but not BPL,” said John.
“Maybe that was it.”
A couple more crashes during the long weekend served to
reinforce John’s friend’s proclamation. Little did John know that he
caused the crash by not range-checking with that big gasoline engine
running. He got the airplane far enough out, and the signal loss was
Low- to medium-level power lines, such as the ones shown,
may someday carry BPL signals. Photo courtesy ARRLWeb.
There are various manufacturers of BPL systems, and they do look
different. The big giveaway is large clamps that connect to topmost
lines on utility poles. Don’t confuse them with utility devices
such as transformers and capacitors that are part of the powerdistribution
system. Photo courtesy ARRLWeb.
This continues along the path in a huge network that becomes the
distribution means for Internet service. At the home, a special modem
extracts the signals from the power line and connects to your
computer.
The Federal Communications Commission (FCC) authorized the
testing of these BPL systems in a series of trials during the past few
years. The FCC and BPL manufacturers intentionally kept it quiet;
they did not want to arouse the suspicions of other users of the
frequencies they were utilizing.
Not until late in 2003—when the FCC put out a Notice of Inquiry
(NOI)—did it become evident that some changes were coming. The
NOI indicated that the FCC was going to incorporate the specifics of
BPL under FCC Part 15 rules. Part 15 regulates the output signal
power of unlicensed intentional and unintentional signal radiators,
such as computers and power supplies; somehow the FCC was going
to pigeonhole BPL into this rule.
AMA immediately took action through its attorney and responded
with a letter of objection, as did most others who used the radio bands
that could be affected.
FCC Part 15 was originally intended to regulate the emissions
from sources that are considered “point source radiators.” The
oscillators in your dual-conversion RC receivers, microwave ovens,
television sets, and garage-door openers are governed by this rule. All
of these devices have essentially one point where the emission
occurs.
On the other hand, BPL is a distributed source of radio-frequency
(RF) energy because the BPL signals are transmitted along
unshielded power lines. DSL is shielded with twisted telephone
wires. Cable service is protected with a braided shield. BPL is
transmitted along bare wires that were meant to transmit 60-hertz AC
(alternating current) power—not the many MHz of broadband RF
signals.
Although BPL was “technically” already allowable under FCC
Part 15, there were no specific rules and requirements. The BPL
manufacturers needed the specifics added to proceed with
deployment.
The potential problem with BPL is that the signals don’t stay
within the power line, as they do in cable broadband technology. The
power line radiates the signal like a big, old antenna. How far away
from the power line the signal is going to bother other services is a
source of contention and much debate among the users and the FCC.
BPL is authorized to operate on frequencies between 1.8 MHz and
80.0 MHz. This is above the AM (Amplitude Modulation) broadcast
band and below the FM (Frequency Modulation) broadcast band.
Meet Dan Williams
Dan Williams has been into aircraft modeling
since he was very young and has been active in RC
since 1979. He has been a licensed radio amateur
since 1977.
Dan graduated in 1980 from Clarkson College of
Technology (Potsdam NY) with a bachelor’s of
science degree in electrical engineering,
specializing in communication systems. He
obtained an FCC Commercial Radiotelephone
License in 1981 and has been involved in RCsystem
operation and repair since then.
In 1999 Dan became frequency coordinator for
AMA District II. In 2003 he was appointed to the
AMA Frequency Committee, where he has joined
the ongoing investigation into the impact of BPL
and new RC technologies on the future of RC
modeling. MA
Our airborne RC operations are in the 72
MHz band, near the upper end of the
allowable spectrum for BPL. The few
frequencies available on 27 MHz in the
Citizens’ Band (CB), some inexpensive
systems on 49 MHz, and licensed Handheld
Amateur Radio (HAM) operators who can
use the 50 MHz and 53 MHz frequencies for
RC are also affected.
Most RC modelers use our exclusive 50
frequencies in the 72 MHz band. Currently
the state-of-the-art BPL systems being
deployed in the test sites are operating
between 1.8 MHz and roughly 30.0 MHz—
well below our normally used RC band.
Early in 2004 the FCC put out a Notice
of Proposed Rulemaking (NPRM), which
meant that it was intending to move ahead
with BPL incorporation into FCC Part 15.
AMA, along with its attorney, drafted an
extensive letter outlining our objections to
the rulemaking.
The Amateur Radio Relay League
(ARRL—the HAM version of the AMA) has
done exhaustive impact studies on its
operations and included some serious
technical details in the report. We have been
in continual contact with the ARRL and its
engineering staff, and we have basically
aligned AMA with the ARRL to pool our
memberships on this issue.
As a result, the ARRL has provided us
with much more information about the tests
underway and the studies done. This has
been incredibly valuable in the effort to fight
BPL. This will also support our licensed
HAM operators who use the Six Meter band
for RC modeling.
In the NPRM, the FCC outlined a series
of tests that would be used to govern the
emissions from the BPL systems. At a given
distance and height away from the power
lines, the signal level would have to be
below the limit for FCC Part 15 emissions
from unlicensed equipment.
AMA is in the process of determining
whether or not those levels could be a
problem with our modeling operations. The
dilemma is that right now the BPL
equipment isn’t using the whole allotment of
frequencies. Testing our equipment for
compatibility with these systems has been
impossible.
We’ve attempted to do some tests on the
27 MHz band (CB) with equipment on the
few CB frequencies we have, but the results
have been inconclusive. Some BPL systems
have been “notching out,” or trying to limit
the amount of power used in the CB
frequencies. It has been difficult for AMA to
determine the effects.
October 28, 2004, the FCC released a
Rule and Order (RO). It made BPL official!
The order basically outlines everything that
was previously stated in the NPRM, with
several crucial and notable exceptions.
First, the equipment used for BPL must
be “certified” to meet FCC standards. This
was a big hit against the BPL manufacturers.
Now they must prove that the equipment
meets the standards rather than just verify it
or state that it does.
Second, the installer must verify the
equipment, indicating that it meets the Part
15 requirements. This means that the
equipment installer must ensure that it
doesn’t exceed the limits. All of the
providers must have test equipment available
to do the checking at the installation site.
This prevents installers from arbitrarily
“turning up” the power to make a particular
stubborn installation work.
I should point out that the BPL
manufacturers wanted a higher limit put in
place to make the system more reliable, but
the FCC didn’t give it to them.
Third, a public database must be kept of
all BPL installations, such that anyone can
determine exactly where a BPL system has
been deployed. Until now, the test sites have
been kept under tight wraps so that the BPL
opponents couldn’t easily scrutinize their
operation. The manufacturers and providers
really did not want this put into the ruling.
Those three points were advanced by the
Academy in its filings in an effort to exercise
some control over BPL operations. In
addition, BPL is only authorized to exist
through what is referred to as “license by
rule.” This is the same condition which
exists for our operations. Therefore, BPL is
required to cease operations if it interferes
with licensed operations.
These conditions serve to protect
everyone to a greater degree and actually
make BPL a “harder sell” when trying to
compete with cable or DSL.
What does all of this mean for us? The AMA
Frequency Committee viewed the small list of
test sites currently in operation. There has
been no widespread deployment of BPL to
date. There were only roughly a dozen
systems being tested, and they were limited in
size and scope. These sites were within
suburbs or small city areas, and not where the
average modelers would be flying their
airplanes.
BPL is only to be used in medium-voltage
lines, or the typical power lines that run down
the road in neighborhoods. It is not being used
in the high-voltage distribution lines. Many
model sites are within sight of some of these
towering “megavoltage” power lines; rest
assured that BPL will not be found here.
As of this writing, several of the dozen or
so systems that have been used for testing
have been shut down for various reasons.
Some companies have found that the return is
not worth the investment. Many studies show
that BPL is not the “cash cow” for providers
and utilities they thought it would be.
In some places, BPL just plain doesn’t
work well. Every several hundred feet, a new
repeater injector has to be installed on the
power lines to keep the signal going. This is a
cost issue. In many places, simple power-line
noise is causing grief for installers. They
cannot turn up the power to make things
work, so there are those places that can’t
receive BPL signals at all.
HAM-radio communicators have been
beating on the BPL providers in their areas.
HAM radio for communications has a real
problem in that the signals are weak by
nature, and they’re having a tough time
coping with the signal levels from BPL.
These communication signal levels are way
below the levels used for RC operations.
There has been such an outcry among the
HAM-radio community that some of the
providers find that the investment is not worth
the aggravation. This brings up another point
for us: signal levels.
Members of the AMA Frequency
Committee have been working with the
mathematics and system modeling studies to
see if these FCC Part 15 levels would really
be a problem for us. The jury is still out, but
initial indications are that the signals from our
transmitters are much stronger at quite some
distance from the receivers than the BPL
signals. Therefore, BPL may not be a concern
at all.
Theoretically, an RC receiver a half-mile
away from its transmitter and 30 feet from
power lines will have twice as much RC
signal as a BPL signal would produce. This
means that a model would have to be a halfmile
away and 60 feet or lower in altitude
directly above power lines containing BPL
signals for there to be any potential
interference.
It is doubtful that anyone would fly a
model that far away and that close to the
ground because of visual constraints,
especially near power lines. One can fly that
far away, but only if the model is at a higher
altitude.
Using the same figure of merit with
theoretical signal levels, a model that’s half of
that distance will have four times the RC
signal at the receiver. A quarter mile is a more
realistic distance for most sport-flying. Flying
at a 60-foot altitude a quarter-mile away is an
extreme case, so is there a problem?
Right now we don’t think so. A park flyer
may very well be flown within 60 feet of a
power line, but the transmitter is going to be
much closer to the receiver as well. There is
plenty of signal strength from the transmitter
for the receiver to lock onto.
This doesn’t take into account path losses.
Many assumptions are being made on both
sides of that issue. The modeling of a BPL
system radiation pattern is not trivial, and
there are numerous arguments taking place
about this.
There are conflicting results from studies
being done. One study indicates that after
approximately 100 feet from the power line,
the BPL signal level will be below the
background noise level. HAM-radio
communicators who have experienced BPL
interference firsthand beg to differ. However,
we have to be careful in comparing this to our
RC situation.
As time goes on, the BPL systems will
improve. They have to in order to overcome
the problems they have within their own
systems. They will have to improve their
systems just to compete against the other
modes of high-speed Internet service
already in existence. This will help serve the
other users of the bands too.
Late last summer I was involved in an
investigation of interference to RC
operations at a high-profile meet. Some
people at the event were certain that BPL
was the culprit, and that rumor spread on
the Internet like wildfire.
AMA set out with equipment in tow to
see what the problem was. We found an
extremely quiet 72 MHz RC band; we
didn’t find any BPL! According to our
attorney and other sources, BPL was not
being tested anywhere near this area, and
there was certainly nothing on our 72 MHz
band to indicate otherwise. We also found
a complete lack of any other meaningful
commercial activity.
Modelers are the primary users of 50
individual 72 MHz RC frequencies. They
are assigned by the FCC only for modelaircraft
operation. This assignment was the
direct result of AMA action taken in the
early 1980s.
However, the whole 72 MHz band does
not belong to us! We operate interstitially
with other users in between our
frequencies. Pager transmitters are the big
users and can be a source of trouble. I
bring this up because some will blame
BPL because of pager transmitters.
Is BPL a big problem for our future? It’s
going to be hard to prove false without
conclusive testing with BPL systems in
the 72 MHz band, but indications are that
it will not be a significant issue. The AMA
Frequency Committee is continuing the
investigation. It is certain that BPL will
continue to be the blame for
malfunctioning RC equipment, bad
installations, and dumb thumbs!
BPL deployment has been slowed by
the results of the testing and the
regulations that have been put in place.
Economics will also play a big role in the
slow pace of BPL as cable and DSL
Internet services continue to shore up their
position as established providers. Some
economic indicators are showing that BPL
is just not good business.
Would I hold off on buying RC
equipment on 72 MHz because of BPL?
Most certainly not. Each RC manufacturer
is making absolutely sure that its
equipment is the latest and greatest and
will prevent even the remote chance that
BPL could interfere. That’s good business
and good for RC.
Where do we go from here? The IEEE
(Institute of Electrical and Electronics
Engineers) has been tasked with coming
up with a set of standards for BPL
manufacturers and their operations. The
AMA Frequency Committee and the
ARRL have a vote on that committee to
protect licensed users. We’ve done all we
can legally with regard to filings as far as
the FCC is concerned, with one exception.
Once the RO is printed in the Federal
Registry, it is possible to file for
reconsideration. However, doing so would
require substantial proof that BPL poses a
significant threat. Such proof is
unavailable and is unlikely to be available
as long as BPL is operated strictly within
the FCC Part 15 rules.
Be assured that AMA will continue
working to protect our frequencies just as
it did when they were obtained for the RC
community! MA
Dan Williams
27 Treeline Dr.
Liverpool NY 13090
[email protected]
Edition: Model Aviation - 2005/04
Page Numbers: 73,74,76,78,80
caused by interference from metal-to-metal noise in the linkage. The
other crashes that weekend were caused by “dumb-thumb”
maneuvers.
However, the damage was done. That field was labeled as having
a problem with BPL when BPL was nowhere nearby.
Loss of control is usually followed by placing blame on someone
or something beyond your influence. It’s human nature to say, “I
sure didn’t cause the crash; it must have been something else.” BPL
is the latest buzzword, and it is causing quite a stir. What is BPL?
Can it cause you problems?
Please take some time to read this. I know that technobabble can
glaze people’s eyes over faster than warm milk, but try to read on;
I’ll keep it to a minimum. It is important that everyone understand
the basics of what BPL is, what it is not, and what it can and cannot
do to us as modelers.
Broadband Over Power Lines, Access
BPL, or just plain BPL, is part of what is
generally known as power-line
communications. Utility companies have
used power-line communications for years,
to communicate telemetry between sites.
In BPL, Internet communication signals
are transmitted through the power lines and
are fed into the home. It is a high-speed
form of Internet service, much as cable
Internet service or Digital Subscriber Line
(DSL) phone-line Internet service.
At the head end of the line, the Internet
communication service connects to the
power lines using wireless to talk to a box
up on the utility pole. This box is called an
injector, and out of it come some highvoltage
clamps that “inject,” or magnetically
couple, the signals onto the power line. At
various points along the lines, the signal is
extracted, amplified, repeated through
wireless, and reinjected into the next section
of power lines.
by Dan Williams
Injector connected to pole and power line injects and removes
BPL signals from power lines. Photo courtesy ARRLWeb.
Does your model field have some of these structures (on the left) nearby? Rest assured
that BPL won’t be found anywhere near them. Photo courtesy the author.
JOHN JUST FINISHED his pride and joy: a Stand-Off Scale P-
51D Mustang. When he arrived at the field, he picked up the
frequency pin and his transmitter. Once the preflight checks were
completed, including a range check, John figured he was “good to
go.”
He was the only one on the flightline; all other transmitters were
in the impound. Everyone seemed captivated while watching the
maiden flight. After a bit of trimming during the first few passes, the
model was flying well. John let the dogs out and ripped a few rolls!
All was fine with the world.
With its gasoline engine sounding sweet, John decided to take
the P-51 up high and way out to set up for a big ol’ victory roll. He
rolled the model inverted and began a Split S. Suddenly there was a
twitch of the tail. Then another! In desperation, John yelled “I ain’t
got it!”
There was a sickening crunch as “Six Shooter” buried itself in
the ground way off the edge of the runway. “Somebody shot me
down!” John moaned. But as he looked around, he saw that
everyone was standing around the pits, nowhere near the impound.
All of the transmitters were there and were off. No one knew what to
say, but everyone headed out to the crash site to help with the
pickup.
“Something happened; I had no control at all,” John related.
“Ah, it must have been BPL,” said one of John’s buddies as they
walked. “I heard those systems are going in everywhere and they’re
causing crashes all over the country. That must’ve been what
happened.”
“Huh? I’ve heard of pagers and stuff, but not BPL,” said John.
“Maybe that was it.”
A couple more crashes during the long weekend served to
reinforce John’s friend’s proclamation. Little did John know that he
caused the crash by not range-checking with that big gasoline engine
running. He got the airplane far enough out, and the signal loss was
Low- to medium-level power lines, such as the ones shown,
may someday carry BPL signals. Photo courtesy ARRLWeb.
There are various manufacturers of BPL systems, and they do look
different. The big giveaway is large clamps that connect to topmost
lines on utility poles. Don’t confuse them with utility devices
such as transformers and capacitors that are part of the powerdistribution
system. Photo courtesy ARRLWeb.
This continues along the path in a huge network that becomes the
distribution means for Internet service. At the home, a special modem
extracts the signals from the power line and connects to your
computer.
The Federal Communications Commission (FCC) authorized the
testing of these BPL systems in a series of trials during the past few
years. The FCC and BPL manufacturers intentionally kept it quiet;
they did not want to arouse the suspicions of other users of the
frequencies they were utilizing.
Not until late in 2003—when the FCC put out a Notice of Inquiry
(NOI)—did it become evident that some changes were coming. The
NOI indicated that the FCC was going to incorporate the specifics of
BPL under FCC Part 15 rules. Part 15 regulates the output signal
power of unlicensed intentional and unintentional signal radiators,
such as computers and power supplies; somehow the FCC was going
to pigeonhole BPL into this rule.
AMA immediately took action through its attorney and responded
with a letter of objection, as did most others who used the radio bands
that could be affected.
FCC Part 15 was originally intended to regulate the emissions
from sources that are considered “point source radiators.” The
oscillators in your dual-conversion RC receivers, microwave ovens,
television sets, and garage-door openers are governed by this rule. All
of these devices have essentially one point where the emission
occurs.
On the other hand, BPL is a distributed source of radio-frequency
(RF) energy because the BPL signals are transmitted along
unshielded power lines. DSL is shielded with twisted telephone
wires. Cable service is protected with a braided shield. BPL is
transmitted along bare wires that were meant to transmit 60-hertz AC
(alternating current) power—not the many MHz of broadband RF
signals.
Although BPL was “technically” already allowable under FCC
Part 15, there were no specific rules and requirements. The BPL
manufacturers needed the specifics added to proceed with
deployment.
The potential problem with BPL is that the signals don’t stay
within the power line, as they do in cable broadband technology. The
power line radiates the signal like a big, old antenna. How far away
from the power line the signal is going to bother other services is a
source of contention and much debate among the users and the FCC.
BPL is authorized to operate on frequencies between 1.8 MHz and
80.0 MHz. This is above the AM (Amplitude Modulation) broadcast
band and below the FM (Frequency Modulation) broadcast band.
Meet Dan Williams
Dan Williams has been into aircraft modeling
since he was very young and has been active in RC
since 1979. He has been a licensed radio amateur
since 1977.
Dan graduated in 1980 from Clarkson College of
Technology (Potsdam NY) with a bachelor’s of
science degree in electrical engineering,
specializing in communication systems. He
obtained an FCC Commercial Radiotelephone
License in 1981 and has been involved in RCsystem
operation and repair since then.
In 1999 Dan became frequency coordinator for
AMA District II. In 2003 he was appointed to the
AMA Frequency Committee, where he has joined
the ongoing investigation into the impact of BPL
and new RC technologies on the future of RC
modeling. MA
Our airborne RC operations are in the 72
MHz band, near the upper end of the
allowable spectrum for BPL. The few
frequencies available on 27 MHz in the
Citizens’ Band (CB), some inexpensive
systems on 49 MHz, and licensed Handheld
Amateur Radio (HAM) operators who can
use the 50 MHz and 53 MHz frequencies for
RC are also affected.
Most RC modelers use our exclusive 50
frequencies in the 72 MHz band. Currently
the state-of-the-art BPL systems being
deployed in the test sites are operating
between 1.8 MHz and roughly 30.0 MHz—
well below our normally used RC band.
Early in 2004 the FCC put out a Notice
of Proposed Rulemaking (NPRM), which
meant that it was intending to move ahead
with BPL incorporation into FCC Part 15.
AMA, along with its attorney, drafted an
extensive letter outlining our objections to
the rulemaking.
The Amateur Radio Relay League
(ARRL—the HAM version of the AMA) has
done exhaustive impact studies on its
operations and included some serious
technical details in the report. We have been
in continual contact with the ARRL and its
engineering staff, and we have basically
aligned AMA with the ARRL to pool our
memberships on this issue.
As a result, the ARRL has provided us
with much more information about the tests
underway and the studies done. This has
been incredibly valuable in the effort to fight
BPL. This will also support our licensed
HAM operators who use the Six Meter band
for RC modeling.
In the NPRM, the FCC outlined a series
of tests that would be used to govern the
emissions from the BPL systems. At a given
distance and height away from the power
lines, the signal level would have to be
below the limit for FCC Part 15 emissions
from unlicensed equipment.
AMA is in the process of determining
whether or not those levels could be a
problem with our modeling operations. The
dilemma is that right now the BPL
equipment isn’t using the whole allotment of
frequencies. Testing our equipment for
compatibility with these systems has been
impossible.
We’ve attempted to do some tests on the
27 MHz band (CB) with equipment on the
few CB frequencies we have, but the results
have been inconclusive. Some BPL systems
have been “notching out,” or trying to limit
the amount of power used in the CB
frequencies. It has been difficult for AMA to
determine the effects.
October 28, 2004, the FCC released a
Rule and Order (RO). It made BPL official!
The order basically outlines everything that
was previously stated in the NPRM, with
several crucial and notable exceptions.
First, the equipment used for BPL must
be “certified” to meet FCC standards. This
was a big hit against the BPL manufacturers.
Now they must prove that the equipment
meets the standards rather than just verify it
or state that it does.
Second, the installer must verify the
equipment, indicating that it meets the Part
15 requirements. This means that the
equipment installer must ensure that it
doesn’t exceed the limits. All of the
providers must have test equipment available
to do the checking at the installation site.
This prevents installers from arbitrarily
“turning up” the power to make a particular
stubborn installation work.
I should point out that the BPL
manufacturers wanted a higher limit put in
place to make the system more reliable, but
the FCC didn’t give it to them.
Third, a public database must be kept of
all BPL installations, such that anyone can
determine exactly where a BPL system has
been deployed. Until now, the test sites have
been kept under tight wraps so that the BPL
opponents couldn’t easily scrutinize their
operation. The manufacturers and providers
really did not want this put into the ruling.
Those three points were advanced by the
Academy in its filings in an effort to exercise
some control over BPL operations. In
addition, BPL is only authorized to exist
through what is referred to as “license by
rule.” This is the same condition which
exists for our operations. Therefore, BPL is
required to cease operations if it interferes
with licensed operations.
These conditions serve to protect
everyone to a greater degree and actually
make BPL a “harder sell” when trying to
compete with cable or DSL.
What does all of this mean for us? The AMA
Frequency Committee viewed the small list of
test sites currently in operation. There has
been no widespread deployment of BPL to
date. There were only roughly a dozen
systems being tested, and they were limited in
size and scope. These sites were within
suburbs or small city areas, and not where the
average modelers would be flying their
airplanes.
BPL is only to be used in medium-voltage
lines, or the typical power lines that run down
the road in neighborhoods. It is not being used
in the high-voltage distribution lines. Many
model sites are within sight of some of these
towering “megavoltage” power lines; rest
assured that BPL will not be found here.
As of this writing, several of the dozen or
so systems that have been used for testing
have been shut down for various reasons.
Some companies have found that the return is
not worth the investment. Many studies show
that BPL is not the “cash cow” for providers
and utilities they thought it would be.
In some places, BPL just plain doesn’t
work well. Every several hundred feet, a new
repeater injector has to be installed on the
power lines to keep the signal going. This is a
cost issue. In many places, simple power-line
noise is causing grief for installers. They
cannot turn up the power to make things
work, so there are those places that can’t
receive BPL signals at all.
HAM-radio communicators have been
beating on the BPL providers in their areas.
HAM radio for communications has a real
problem in that the signals are weak by
nature, and they’re having a tough time
coping with the signal levels from BPL.
These communication signal levels are way
below the levels used for RC operations.
There has been such an outcry among the
HAM-radio community that some of the
providers find that the investment is not worth
the aggravation. This brings up another point
for us: signal levels.
Members of the AMA Frequency
Committee have been working with the
mathematics and system modeling studies to
see if these FCC Part 15 levels would really
be a problem for us. The jury is still out, but
initial indications are that the signals from our
transmitters are much stronger at quite some
distance from the receivers than the BPL
signals. Therefore, BPL may not be a concern
at all.
Theoretically, an RC receiver a half-mile
away from its transmitter and 30 feet from
power lines will have twice as much RC
signal as a BPL signal would produce. This
means that a model would have to be a halfmile
away and 60 feet or lower in altitude
directly above power lines containing BPL
signals for there to be any potential
interference.
It is doubtful that anyone would fly a
model that far away and that close to the
ground because of visual constraints,
especially near power lines. One can fly that
far away, but only if the model is at a higher
altitude.
Using the same figure of merit with
theoretical signal levels, a model that’s half of
that distance will have four times the RC
signal at the receiver. A quarter mile is a more
realistic distance for most sport-flying. Flying
at a 60-foot altitude a quarter-mile away is an
extreme case, so is there a problem?
Right now we don’t think so. A park flyer
may very well be flown within 60 feet of a
power line, but the transmitter is going to be
much closer to the receiver as well. There is
plenty of signal strength from the transmitter
for the receiver to lock onto.
This doesn’t take into account path losses.
Many assumptions are being made on both
sides of that issue. The modeling of a BPL
system radiation pattern is not trivial, and
there are numerous arguments taking place
about this.
There are conflicting results from studies
being done. One study indicates that after
approximately 100 feet from the power line,
the BPL signal level will be below the
background noise level. HAM-radio
communicators who have experienced BPL
interference firsthand beg to differ. However,
we have to be careful in comparing this to our
RC situation.
As time goes on, the BPL systems will
improve. They have to in order to overcome
the problems they have within their own
systems. They will have to improve their
systems just to compete against the other
modes of high-speed Internet service
already in existence. This will help serve the
other users of the bands too.
Late last summer I was involved in an
investigation of interference to RC
operations at a high-profile meet. Some
people at the event were certain that BPL
was the culprit, and that rumor spread on
the Internet like wildfire.
AMA set out with equipment in tow to
see what the problem was. We found an
extremely quiet 72 MHz RC band; we
didn’t find any BPL! According to our
attorney and other sources, BPL was not
being tested anywhere near this area, and
there was certainly nothing on our 72 MHz
band to indicate otherwise. We also found
a complete lack of any other meaningful
commercial activity.
Modelers are the primary users of 50
individual 72 MHz RC frequencies. They
are assigned by the FCC only for modelaircraft
operation. This assignment was the
direct result of AMA action taken in the
early 1980s.
However, the whole 72 MHz band does
not belong to us! We operate interstitially
with other users in between our
frequencies. Pager transmitters are the big
users and can be a source of trouble. I
bring this up because some will blame
BPL because of pager transmitters.
Is BPL a big problem for our future? It’s
going to be hard to prove false without
conclusive testing with BPL systems in
the 72 MHz band, but indications are that
it will not be a significant issue. The AMA
Frequency Committee is continuing the
investigation. It is certain that BPL will
continue to be the blame for
malfunctioning RC equipment, bad
installations, and dumb thumbs!
BPL deployment has been slowed by
the results of the testing and the
regulations that have been put in place.
Economics will also play a big role in the
slow pace of BPL as cable and DSL
Internet services continue to shore up their
position as established providers. Some
economic indicators are showing that BPL
is just not good business.
Would I hold off on buying RC
equipment on 72 MHz because of BPL?
Most certainly not. Each RC manufacturer
is making absolutely sure that its
equipment is the latest and greatest and
will prevent even the remote chance that
BPL could interfere. That’s good business
and good for RC.
Where do we go from here? The IEEE
(Institute of Electrical and Electronics
Engineers) has been tasked with coming
up with a set of standards for BPL
manufacturers and their operations. The
AMA Frequency Committee and the
ARRL have a vote on that committee to
protect licensed users. We’ve done all we
can legally with regard to filings as far as
the FCC is concerned, with one exception.
Once the RO is printed in the Federal
Registry, it is possible to file for
reconsideration. However, doing so would
require substantial proof that BPL poses a
significant threat. Such proof is
unavailable and is unlikely to be available
as long as BPL is operated strictly within
the FCC Part 15 rules.
Be assured that AMA will continue
working to protect our frequencies just as
it did when they were obtained for the RC
community! MA
Dan Williams
27 Treeline Dr.
Liverpool NY 13090
[email protected]