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[RFI] BPL video FAQs

To: <rfi@contesting.com>
Subject: [RFI] BPL video FAQs
From: wx3k at ptd.net (Stephanie WX3K)
Date: Sat Aug 9 01:56:37 2003

Nice job on the video.....The segment showing the TS-440s on the table with
the S9 noise level is quite alarming to say the least.

I would assume that PP&L was the one utility conducting BPL trials. Correct
?.....I am a PP&L customer here in the Poconos and I have spoken to the
folks at PP&L many times about local RFI in my neighborhood. I took my Yaesu
FT-817 out with my SONY camcorder and recorded the resultant RFI levels and
sent them a copy of the videotape. They understand that when I call with an
RFI complaint, I mean buisness now ;-)

If there is anything I can do to help your effort, please let me know.....I
am an experienced engineer and have a significant amount of experience
chasing down RFI......

Stephanie R. Koles WX3K
wx3k at arrl dot net

-----Original Message-----
From: rfi-bounces@contesting.com [mailto:rfi-bounces@contesting.com]On
Behalf Of Hare,Ed, W1RFI
Sent: Friday, August 08, 2003 9:23 PM
To: rfi@contesting.com
Subject: [RFI] BPL video FAQs

Hi, guys and gals,

Well, it was me that done it, with the help of 160,000 hams who have helped
make sure ARRL has resources to do this sort of thing.  Thanks to all who
helped make it happen. I couldn't have done it without you.

In a number of lists, a number of questions have come up.

Q:  The video is a bit rough.  Putting a radio in a car and driving around
is not very high tech.  Why did you do it this way?
A:  ARRL has submitted a 120-page paper to the FCC.  Appendix C of that
paper calculates the interference potential from Part 15 radiated emissions
limits.  This video study accomplished just what it intended.  It
demonstrated that systems whose emissions are at the FCC emissions limits
have a significant impact on HF communications.  When the video was put
together last Friday, the reply comment date was August 6, so ARRL did a
fast job that was just sufficient to that task, if accompanied by
explanation.  With the extended timeline, there is more time to do a better
job of editing a "non-ham" version, with an A/B comparison showing non-BPL
areas and just a bit of voiceover on the video, as well as the expected
written explanation.  But ARRL expected that the video be understood by hams
"as is" and wanted to get this information into the hands of the amateur
community soonest.

Q: How representative of what you found was the video?
A:  I ran about 3 hours worth of video, and believe that what is on the
version on the web is a fair representation of what interference levels that
I found.  If the S meter levels were S5, then that is what we showed.  If we
found interference on 5.3 MHz, that is what was shown. The systems were
visted at different times of day, so in some cases, with most people at
work, the usage of the system was light.   In doing two long drives showing
the levels not changing much with distance, I think the video communicates
that I did not go looking for hot spots.  The system in an area of
underground wiring did exhibit less noise level than the systems with BPL
signals on overhead lines.  In a few cases, the stronger amateur signals
were copyable, although it sure wasn't pleasant copy. The ones on the tape
were actually S9, and would have been Q5 except for the noise.

Q:  Was that noise from your car?
A:  Only at a level well below what was being observed.  The 89 Subaru has a
computer, but it is off when the ignition switch is off, and most of the
test  were done parked, with the engine off.  When in motion, I have up to
an S5 or S6 ignition noise, but I only made tests in motion where the BPL
noise was much higher. I am an experienced HF mobile operator, so I have a
good understanding of what to expect in mobile installations, and what was
seen on the tape wasn't normal mobile "noise."  Nor was I parked next to the
7/11 with the microwave running. What was observed was pretty consistent in
the test areas, especially the two where I took a good long drive down the

Q: Why does it sound like ignition noise or power-line noise?
A:  The very fast pops heard are the keep-alive pulses from the modem, or
brief bursts of download.  Note that even under those circumstances, an
occasional longer burst is heard.  Unlike auto ignition, which would be very
regularly, these were almost random in timing.  I have also heard these
systems with longer downloads, and that ignition-noise sounding popping is
light compared to how strong it can get on the particular systems involved.
The system with the stronger buzzy sound is from a larger number of modems,
on a different system at a different time of day.  It is much more irregular
than power-line noise and when analyzed, lacks 60- and 120-Hz peaks. I also
noted that as I drove within the area, it was constant along a long stretch
of road, something that doesn't happen with power-line noise, and when I
drove outside the test area, it diminished smoothly.

Q: Some of the noise was only S4 or so. That isn't that bad.
A:  It sure would be for this QRPer. In a quiet location, the ambient noise
level is 10s of dB lower than S4.  Also, in some cases, the short pulses
really didn't get the S meter swinging.  You may note that the S meter jumps
a few units during the louder bursts.

Q:  My power line noise is stronger than that.  Why is this a problem.
A:  If you have S9 power-line noise, you are suffering noise that is clearly
harmful interfence.  You should contact Mike Gruber, W1MG@arrl.org and ask
him to help.  With ARRL's help, the FCC has sent over 30 companies a custom
version of the "power-line letter."

Q:  Did the noise blanker help?
A:  Sometimes.  I observed that on some frequencies, the noise blanker did
something, while on others, it did nothing at all. In any case, a noise
blanker is not a panacea, and when I listened to a signal and used the noise
blanker, it clearly resulted in a muffled and distorted signal. And, as
traffic useage increases on the network, it would be so continuous that a
noise blanker would have less and less effect.

Q:  Why are some of the receivers tuned outside the ham bands?
A:  There are no standards for the spectrum used by BPL systems. In each
case, I tuned where the signals were.   Some were very heavy in the ham
bands, others were heavy somewhere else.  In some cases, I tuned to 5.3 MHz,
a "round" number near our new allocation, or to WWV.

Q: Why are there not widespread reports of interference from these systems?
A: These trials are relatively small. In some cases, they have as few as a
dozen homes. The larger are several hundred.  In many cases, there are no
hams at all in the trial area and if there are, they may not be active on
HF, or active at all.  Hams a few blocks away are apt to hear the signals,
but may not know what they are and, if S4 or so, may not be too agressive at
trying to track down the source.

Although this video is not as polished as I would like, it clearly gets the
point across. It is not intended to be absolute measurement, although ARRL
has the capability to make reasonable field-strength measurements.  It is
intended to show the interference potential to amateur stations in the
region, and it does just that.  Though I was close to the power lines, on
the road, this is a legitimate HF amateur installation and with its modest
antenna, it is not much different than I estimate would be heard with a Yagi
50 feet back, at a height of 40 feet or so.

Ed Hare, W1RFI
225 Main St
Newington, CT 06111
Tel: 860-594-0318
Internet: w1rfi@arrl.org
Web: http://www.arrl.org/tis

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