[RFI] Line Noise
EDWARDS, EDDIE J
EDWARDS, EDDIE J" <firstname.lastname@example.org
Fri, 14 Jan 2000 09:20:46 -0600
> -----Original Message-----
> From: Dana Roode [SMTP:K6NR@ARRL.net]
> Anyone have any sage advice about dealing with Line Noise? I've had
> S5-8 QRN on 80 and 160 for years, but now I'm getting strong QRN on
> the higher bands (20-6) at times. Seems like there are multiple noise
> sources, I'm not sure where to start. I haven't read the ARRL RFI
> book line noise chapter for awhile, guess I could start there -
> tracking down the sources of the noise myself seems difficult,
> especially when the lesser noises are not even audible in my portable
> equipment (very audible with the 80m vertical at home, however).
[Ed-K0iL] Is your portable equipment listening on 80M or some other
freq? Line noise intensity and propagation is variable depending on the
frequency you are listening on. The higher you go in freq, the closer you
have to be to the source to hear the noise. And the lower you go in freq,
the farther away from the source the noise can be picked up. Also, noise as
it propagates down the lines can display standing wave characteristics so
that at the spot your vertical is sitting may be seeing a "peak" in the
vertical position, while it is then a "null" in the horizontal position
which may be why the portable doesn't hear anything there. In another spot
in either direction along the line the opposite will be true. But even at a
null a "minimum" of noise can still be heard. If not, you may not be
hearing pwr line noise at all but something else.
Another thing to keep in mind. You can only hear line noise or
other impulse noises on an AM (or SSB) Rcvr. You CANNOT hear it on FM rcvrs
> I'm located in the Southern California urban sprawl, the city of
> Irvine to be exact. Im on a 5000 sf lot, with neighbors all around,
> and new development (retail, commercial) nearby. All of our utilities
> are underground, but there is a high voltage line running down a main
> street a block away. When the loud noise is on, I can drive down that
> line and hear peaks every so often.
[Ed-K0iL] That's the standing waves I described. You're hearing
the conduction and re-radiation of the noise on the line, not the direct
radiation from the source.
There are 3 ways noise is propagated: (1) Direct Radiation from the
source. This can be picked up at very high freqs (100Mhz & up) on AM. (2)
Conduction on a transmission (or Power) line. This re-radiates the noise
energy all along the transmission line since it is not balanced nor
shielded! (3) Induction onto other lines (power, phone, cable) which can
then re-radiate and conduct the noise to new and exciting locations like
your ham shack!
> I've called Southern California Edison, and they've been out twice.
> They can't hear anything in their equipment, and leave. The lesser
> noise they attributed to commercial or residential usage because it is
> never affected by rain.
[Ed-K0iL] Is the lesser noise real broadbanded like the stronger
noise is (I assume), or is it quantized in frequency packets of 40-70Khz or
so. If packetized, this noise may be nearby touch-lamps or other SCR-type
of devices. (I had one that turned out to be in my own house this winter;
an Christmas lights controller that turned the lights on at dusk an off at
dawn. It only made noise with the lights ON! Never found time to play with
it; just took the lights down!) Touch lamp noise packets will repeat every
170Khz or so corresponding to the fundamental of the free-running oscillator
that makes them work. The packets will also have peaks near each end of the
And at what freq are the SCE guys listening for the noise on their
equipment compared to where you are picking it up?! If your picking it up
on HF and they're listening on VHF, then they don't have a clue about
tracking line noise!
> Any tips? Anyone worked with SCE successfully? Is there a private
> expert one can call upon to sort through line noise sources?
[Ed-K0iL] Tip number one: Ensure you have a very good station
ground. This will rule out noise problems caused by a poor or improper
ground. Go to http://www.polyphaser.com and look at their tutorials under
"Technical Info" if you need more info in this area.
Tip number two: Buy the "Interference Handbook" by William R.
Nelson, WA6FQG who is a retired RFI Investigator from (get this!) SCE
Company! Perhaps you could suggest that the new SCE RFI guy buys this book
as well, if he doesn't already have one. You can buy it at ARRL or CQ
bookstores or even at many Ham shops. Read Chapters 4, 5 & 6 thoroughly!
You can read 1-3 later if you find time or interest! The later chapters
cover other RFI topics but some of these are out-dated and the ARRL's RFI
Handbook is better on these topics.
The new ARRL "RFI Handbook" has a good chapter on electrical line
noise written by an RFI guy from NE Utilities. It's much better than the
info in the old book "RFI: How to find it & fix it".
Tip number three: The only way to get the noise fixed is to either
locate the noise yourself, or get the SCE guys to find it, and then have SCE
fix the problem. Unfortunately, along with supposedly lower priced
electricity, deregulation has also brought lowered services. The RFI
investigator is usually the first to go in many deregged utilities across
the nation. They are not spending money on equipment and training like they
used to when they got dozens of calls each day before cable TV came along.
Now the only complaints coming in are from Hams and CBers. No one else uses
wireless "AM" rcvrs anymore.
If you're having problems getting SCE to get going, first make sure
it is in fact power line noise and not SCR devices. Then track it down
using your car's AM radio to narrow down the gross vicinity of the source.
Ignore the peaks and nulls and just look for increasingly stronger peaks.
Once the peaks start getting weaker, that indicates you've driven past the
source or the sources main conduction "FEED". Go back and drive at 90degree
angles from the Peak-Peak location repeating the process. This will get you
"in the neighborhood" of the source.
After doing this you will probably see how difficult this can be and
have some empathy for the poor RFI guy at SCE who probably doesn't have
anymore training at this point than you! %^O
I'll also send you a copy of a recent ARRL bulletin relating to PG&E
getting a little FCC attention as a result of not doing any RFI
investigating. Try contacting the ARRL first (maybe Ed-W1RFI?) before
contacting the FCC. A letter from ARRL might get SCE going on this.
de ed -K0iL
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