Pete,
Just a hunch, but look for something electrical close to the
feedlines or array control lines, or array control logic power
source. If you have to get close to the antennas to hear it
with your portable, it is probably NOT being picked up by the
antennas, but radiated by them.
Cortland
------Original Message------
From: Pete Smith <n4zr@contesting.com>
To: rfi@contesting.com
Sent: January 2, 2001 4:22:06 PM GMT
Subject: [RFI] Tracking down external noise
I'm going a little nuts here. During CQWWCW and thereafter,
my 80m
operations were severely handicapped by intense noise. In the
wide (LSB)
filter position, in daytime, my noise floor is around S9 with
occasional
bursts to S9 + 20-40dB. The bursts sound like a classic
powerline arc, but
the "floor" itself has more of a "frying" sound, punctuated
with occasional
pops that sound like an electric fence, though without a
fence's repetitive
pattern.
The nature of the noise definitely changes as I "rotate" the
antenna (it's
a 4-element dipole parasitic array, mostly vertically
polarized.
Northeast, the floor is S7-9, varying rapidly with pops, and
the bursts are
S9 +20. SE the floor is steady S9 +10 and the bursts are
still S9+20. SW
the floor is S9 + 15 but I don't hear the bursts. Northwest,
the floor is
back down to S9, but steady, but still no bursts.
My suspicion is that I have at least two sources with
different
characteristics, one northeast and one south to southwest. If
this is so,
then I have probably had the eastern noise (the arc) for some
time, but the
frying noise floor to the south is new.
Now here's where it gets complicated. With my portable radio
(a Sony
ICF-SW7600) I cannot hear any of the noise with the whip, and
I can only
hear it with a 25-foot wire antenna attached when I'm close
enough to my
array so that signals are being coupled from the array to the
wire. I can
hear the bursts/arcs at higher frequencies, but the noise
floor is not
there, so I can hear pretty well on my yagis.
I have driven around to the east fairly extensively, but have
never heard
the arcing. The farmer to the south is a real PITA, and is
not likely to
cooperate with any search for a source on his property.
I'm at a loss. Any advice would be much appreciated. I have
a .wav file
recording of the composite noises, made in AM mode, but
hesitate to send it
to anyone because it is fairly large.
Thanks in advance.
73, Pete N4ZR
Contesting is!
The World Contest Station Database
is back up and running at
http://www.qsl.net/n4zr
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