[RFI] Power line RFI situation
EDWARDS, EDDIE J
Mon, 18 Mar 2002 16:23:28 -0600
> -----Original Message-----
> From: Rob Atkinson, K5UJ
> I had taken a stab at it last fall to
> the extent that I naively called the city electrical dept. to complain
> the noise. A young man called back a few hours later to tell me he
> drove around my neighborhood & listened on his car radio for noise and
> didn't hear anything.
Step one for the City: "Give the brush-off and see if they give
up and go away." This is going to be the first hurdle to overcome once
you've found the noisey poles for them.
Was the young man also listening to Talk-radio the whole time
while driving around? Kind of hard to hear noise that's covered up by a
strong nearby station! And all that noise in between stations is just
normal static. (Yea, that's the ticket!)
Of course their perspective is this: "If it doesn't interfere
with AM reception (or TV), it's not a REAL problem." You'll need to
convince them otherwise. Mention that the "harmful interference" you
are getting is NOT on the AM broadcast band, but on SEVERAL Amateur
Radio Service bands. The fact he's not hearing interference to AM
signals has no relation to your problem.
> He suggested I make sure the noise wasn't coming from inside my
> house. I told him okay, and realized this wasn't going to be so easy.
> had figured the noise was from outside because it went away when I
> disconnected by antenna. I got a copy of the ARRL RFI Book and
> started reading it.
Only way to know for sure is to kill the power to your whole
house and then listen on the radio and antenna getting the noise in the
first place. You will need a battery to run the radio.
> One way I know it's from outside my house is that I've observed that
> it goes away when it snows or rains. The rest of the time it's there
> night and day.
Wet snow I assume. If this is a characteristic of the noise,
I'd suspect a wood pole is your main source (there are probably others).
Wood expands when wet; expansion cause loose hardware to become tight
again resulting in NO NOISE.
> Over the weekend I found an old Alinco 2m/70 cm HT that receives air
> band on AM.
> I have it tuned to a bit above 108 Mhz and have also been driving
> around with it connected to a 1/4 w. g.p. on the roof of my car. I've
> a couple of potential sources.
> I went to radio shack yesterday. They sell a cheap 20 buck 6 el. yagi
> for the FM broadcast band. I bought one along with a receive only
> balun and am going to use it to DF the problem with the 108 mhz AM rx.
> St. Charles for several hours noting the possible sources (there's one
> real bad one on the other side of the Fox river from me) then go back
> with the yagi to try to isolate the pole(s). Then contact the city
> electrical dept. & put everything on the table & see what they do.
Be sure not to get faked out by some of the peaks (and nulls)
along the powerline. They have standing waves and you need to determine
which peak out of many is actually the strongest. You may've noticed
that the vertical and horizontal peaks are 180 degrees out of phase. So
always hold the yagi in the same polarization.
A good book to get that shows this and many other good
suggestions for DFing is William Nelson's "Interference Handbook". The
ARRL book you got also has a great chapter on PL noise. You might go to
contesting.com and review some of the archives from this list on the
powerline noise topic. There have been many posts over the last couple
Good luck Rob, we'll be looking for further updates.
de ed -K0iL