So to repeat, how does the average ham, whom you have exhorted to
"make sure it's BPL that you're complaining about", go about detecting
and sorting which is what, given that spectral analysis gear, and the
training to use it if it was available, is virtually nonexistnt in the
average hamshack? Is there a aural signature or more than one for the
different BPL modes? Is the Emmaus test site video/audio clip
reresentative enough to make the call, or is something more needed?

Carl had suggested that those that suspect they have BPL interference contact
me. ARRL can help ask the right questions and analyze the pattern. Many hams
do have the abiltity to use an oscilloscope and may be able to do some
time-domain analysis themselves.

I expect that if it was indeed BPL RFI it would follow the power grid
pretty closely with signal strength highest when close, and tapering off
with distance away from the lines. But from the one report posted here
of a ham who said he heard it from a distance of 60 miles, seems like
propagation will play into the picture-to be expected at HF as all
experienced HF ham operators know. Or maybe *he* mis-identified it!

That is almost certain. At a few hundred homes and BPL power levels, it is not
possible for a small number of signals to propagate by skywave at a level
strong enough to be heard. When there are tens of thousands of simultaneous
signals, that may be *just* possible, but not at all certain.

So who do hams call for assistance, the ARRL? I haven't seen anything
from them suggesting that.

I have just completed the draft of the letter that ARRL will send to hams in
the trial cities, asking for reports and offering to help vet them before they
are sent. It should go out this week.

73,
Ed Hare, W1RFI
ARRL Lab

So who do hams call for assistance, the ARRL? I haven't seen anything
from them suggesting that.

I have just completed the draft of the letter that ARRL will send to hams in
the trial cities, asking for reports and offering to help vet them before
they
are sent. It should go out this week.

73,
Ed Hare, W1RFI
ARRL Lab



If there are RFI complaints, kindly correct me if I am wrong, but I seem to
recall that the FCC has the purview on such matters, not a non-profit
organization.

Ed, is there some reason why radio amateurs cannot document their complaints,
if they exist, to the FCC directly? Why is it preferable to go through a non
profit organization? Is there some additional technical capacity which the
radio amateur requires in order to make an RFI complaint? If so, could you
kindly let us know what that is and how it is accessed?

Many thanks.

73,
Chip N1IR

Ed, is there some reason why radio amateurs cannot document their
complaints,
if they exist, to the FCC directly?

They can, if they are certain that they are documenting BPL and not another
source. It is possible to misidentify other sources as BPL, so having a
time-domain and frequency-domain analysis of the received signal will be an
important cross check.

73,
Ed Hare, W1RFI

They can, if they are certain that they are documenting BPL and not another
source. It is possible to misidentify other sources as BPL, so having a
time-domain and frequency-domain analysis of the received signal will be an
important cross check.

73,
Ed Hare, W1RFI


Good point. Ed, what does a plasma TV look like compared to BPL. Is the
multidomain signature quite different?

73,
Chip N1IR

Good point. Ed, what does a plasma TV look like compared to BPL. Is the
multidomain signature quite different?

I have not looked at a plasma TV, Chip, but I would make that diagnosis
primarily on on the basis of the sphere of influence. In the BPL test areas,
the interference was heard over the entire area that had the BPL couplers in
place.

There are other indicators, too. Knowing the involved BPL manufacturer would
let one pretty easily compare what was heard on the air to the known
characteristics of the BPL system involved. Interference from plasma TVs is not
going to be "modulated" with digital signals, as would a BPL signal. Those
OFDM carriers in the Ambient and Amperion BPL systems would be pretty hard to
confuse with anything else.

Another characteristic to look for is spectral occupancy. If the signal appears
suddenly in spectrum, is heard over several MHz, then suddenly tapers off, that
also matches the BPL characteristics, not that from other devices.

If the signal is noiselike, but clearly digital in sound, one can also look for
the bursts of the downloads, followed by the shorter, "keep alive" pulses that
some of the systems do.

If all of the above added up and started at the same time the BPL system was
brought on line, I would feel comfortable with my diagnosis.

73,
Ed Hare, W1RF

Ed...

Is the ARRL preparing a FAQ for amateurs who have scopes, spectrum
analyzers, or service monitors, etc., as to how they might go about
inspecting a suspected chunk of spectrum and how detect, identify,
qualify whey they see/hear?

73
Dan (K0DAN)

I have not looked at a plasma TV, Chip, but I would make that diagnosis
primarily on on the basis of the sphere of influence. In the BPL test areas,
the interference was heard over the entire area that had the BPL couplers in
place.

There are other indicators, too. Knowing the involved BPL manufacturer would
let one pretty easily compare what was heard on the air to the known
characteristics of the BPL system involved. Interference from plasma TVs is not
going to be "modulated" with digital signals, as would a BPL signal. Those
OFDM carriers in the Ambient and Amperion BPL systems would be pretty hard to
confuse with anything else.

Another characteristic to look for is spectral occupancy. If the signal appears
suddenly in spectrum, is heard over several MHz, then suddenly tapers off, that
also matches the BPL characteristics, not that from other devices.

If the signal is noiselike, but clearly digital in sound, one can also look for
the bursts of the downloads, followed by the shorter, "keep alive" pulses that
some of the systems do.

If all of the above added up and started at the same time the BPL system was
brought on line, I would feel comfortable with my diagnosis.

73,
Ed Hare, W1RF

Is the ARRL preparing a FAQ for amateurs who have scopes, spectrum
analyzers, or service monitors, etc., as to how they might go about
inspecting a suspected chunk of spectrum and how detect, identify,
qualify whey they see/hear?

Not at this time, Dan. I want to talk with amateurs who are going to go into
the trial areas, to share my experiences and to make sure I learn as much as
possible from theirs. FAQs are a great way for beginners to learn about a
subject, but some things are still best left to real dialogue.

73,
Ed Hare, W1RFI

Good point. Ed, what does a plasma TV look like compared to BPL. Is the
multidomain signature quite different?

I have not looked at a plasma TV, Chip, but I would make that diagnosis
primarily on on the basis of the sphere of influence. In the BPL test areas,
the interference was heard over the entire area that had the BPL couplers in
place.

There are other indicators, too. Knowing the involved BPL manufacturer would
let one pretty easily compare what was heard on the air to the known
characteristics of the BPL system involved. Interference from plasma TVs is
not
going to be "modulated" with digital signals, as would a BPL signal. Those
OFDM carriers in the Ambient and Amperion BPL systems would be pretty hard to
confuse with anything else.

Another characteristic to look for is spectral occupancy. If the signal
appears
suddenly in spectrum, is heard over several MHz, then suddenly tapers off,
that
also matches the BPL characteristics, not that from other devices.

If the signal is noiselike, but clearly digital in sound, one can also look
for
the bursts of the downloads, followed by the shorter, "keep alive" pulses
that
some of the systems do.

If all of the above added up and started at the same time the BPL system was
brought on line, I would feel comfortable with my diagnosis.

73,
Ed Hare, W1RF


Hi Ed,

I think a general description of other RFI sources would be helpful for any
radio amateur to make a 'first cut' assessment. It might also help you isolate
the truly legitimate cases of BPL RFI--if and when they exist.

I do have a concern that hams not make too many false alarms. Sounds like you
are on top of the the problem and I wish you the best.

73,
Chip N1IR

I think a general description of other RFI sources would be helpful for any
radio amateur to make a 'first cut' assessment. It might also help you
isolate
the truly legitimate cases of BPL RFI--if and when they exist.

There are several RFI sources that would be the most common ones misidentified
as BPL. The first is "conventional" power-line noise. It is usually
characterized by having a *noisy* 120-Hz component, as the sparking takes place
on the positive and negative peaks of the 60-Hz wave. Another is similar,
occurring from things like lamp dimmers, motor controllers, flourescent lights,
etc. Those sources usually have a 120- or 60-Hz component, but the noise on the
peaks is usually quite a bit less noisy looking.

Switch-mode power supplies can also be noisy, but they generally have noise
that ranges from reasonably coherent (carrier-like) to broad, buzzy clumps of
noise, spaced every N kHz, where N is the free-running rate of the switcher
frequency. N is typically 10-50 kHz or so. Some switchers make noise that is
fairly close to gaussian-distributed noise, with a pretty uniform
distibribution of power vs frequency (power spectral density). One key
diagnostic for a switcher is that the N kHz tends to drift around a bit. A
series of noisy carriers or clumps of noise that are spaced every 15 kHz, for
example, may drift up the band as the unit is turned on and warms up over an
hour or so. If so, it is almost certainly a switcher.

(I do, btw, suspect that the "plasma tv" problem is really a switch-mode
problem, as some amateurs have reported no interference from plasma TVs. On my
long list of things to do is to take the Lab's Icom R-3 receiver to the local
big electronics store and see if I can get some estimates of the noise level
from various equipments.)

Probably the most diagnostic, however, it the distribution of noise signal vs
frequency. BPL is designed to use specific spectrum, and as one tunes a general
coverage receiver from 2 to 80 MHz, its onset will be rather sudden, it will
persist for at least several MHz, then taper off just as abruptly.

I do have a concern that hams not make too many false alarms. Sounds like you
are on top of the the problem and I wish you the best.

There are no guarantees, but I am hoping that by talking to each of the hams
that report BPL interference, between them and me we can reach the correct
conclusion. If things don't add up, I will suggest that it not be reported.
Each report of actual interference is precious right now, and I would be
willing to go to the trial area to verify a questionable case.

Thanks for your interest.

73,
Ed Hare, W1RFI

W1RFI wrote:

I have not looked at a plasma TV, Chip, but I would make that diagnosis
primarily on on the basis of the sphere of influence. In the BPL test areas,
the interference was heard over the entire area that had the BPL couplers in
place.


Hmmm - I wonder ... presumably the BPL couplers are capacitors coupling
appropriate RF from one leg of the power system to the next. Would they
also couple spuriously-generated RF at similar frequencies? (yeah, I'm
sure the couplers are more involved than simple RF bypass caps - that's
not the question here.)

The PPL rep accused you of mis-interpreting the RF from a neon sign as a
BPL signal. What DOES happen to the hash generated by a neon sign, then?
is it propagated through the power grid much further when BPL couplers
are present? How about other sources of broadband noise, like loose wires,
arcing insulators, etc? Will the entire BPL scheme spread all these other
spurious emissions far and wide?

And, by the way, since aircraft use AM, do they receive hash when they
fly over BPL lines? Are our brethren in aviation potentially useful
allies in this war?

Bob, KI8AB