At 08:55 PM 10/6/01 +0100, Pete wrote:
>I've been plaqued with powerline type noise now for abt 2 weeks daily.Seems
>if I pass my shortwave portable shortwave antenna near the
>verticals,towers,guy wires,beverages,pennants etc. everthing seems to
>be"hot" and radiating noise.Some thing a lot more than others.Is there a
>method to finding the noisy culprit.I have recently put up a 2 ele 80 mtr
>parasitic array but that was up put up abt a month ago and the problem seems
>to have started in the last 2 weeks.Th inv L elements are open at the
>feedpoint and they are very"hot". I also seem to have one guy wire that
is much hotter than and of the others on the 2 towers.Tnx Pete NO2R
I think this basically just means that your array is working, and provides
a beautiful demonstration of the ability of towers and other conductors to
reradiate noise. I have a 4-element wire parasitic array, and shortly
after it went up I had an experience exactly like yours. I went out with a
shortwave portable and couldn't tell anything about the bearing to the
noise as long as I was close to the antenna. As I moved away from it,
though, the noise fell off quickly to zero, and then, in one direction, it
started to build again. I kept shortening the telescoping antenna to keep
the AGC from confusing things, and followed it right to a neighbor's house
and the infamous thermostatically-controlled dog dish.
You can verify that it is line noise by receiving it on AM and putting a
scope on the audio. The 60 Hz period sticks out like a sore thumb.
So the moral is, if you can use your array's directivity to establish the
rough bearing to the source, fine. If not, get outside the antenna's very
near field and fish for noise, then follow it to the source. Chances are
it is very close.
There is a lot of useful information on the reflector rfi@contesting.com.
www.contesting.com also has an excellent "list search" capability that lets
you search one or all of their lists for keywords, not only in titles but
in the text of messages. A great reference.
Good hunting!
73, Pete N4ZR
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