[RFI] Tracking down external noise

Pete Smith Pete Smith <n4zr@contesting.com>
Tue, 02 Jan 2001 11:22:06 -0500

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

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
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