I have some more data points in my search to eliminate noise in several
of my beverage wires. First, I disconnected both the west and the
southwest beverage wires from my matching transformer box out at the end
of the rx feedlines. I left the coax still connected to the
transformer. I saw two different levels of noise on the wires. One was
at about -135 while the other was below -140 and was almost the
background noise of the receiver all by itself. It appears that a small
amount of noise is coming in on one of the the coax feedlines, and I am
working on building up some 1:1 coax choke baluns to install in the line
where the coax enters the building to remedy this.
I left the West beverage disconnected last night and looked at
the residual noise level there during night time conditions. The noise
stayed at -142 all night, so there was no more pickup than I was getting
during the daytime. What I did discover, was that the night time noise
on the hooked up SW beverage is all over the lot depending on when I
check it. I am now convinced that I am suffering from some unwanted RFI
that seems to only occur at night. It does not affect my other wires,
just west and southwest. It does not sound like power line noise. It
sounds "smoother" and almost natural. I saw noise levels jump from -120
up to almost -100. A typical increase in noise from day to night seems
to be about 10 dB on my other beverage wires, but I am seeing 20 or 30
dB on these two beverages, so something is screwy here.
It looks like moving the beverages away from the vertical antenna
by another 100 ft or so helped out by about 10 dB, but at times they are
still so noisy as to be worthless to use. I tried detuning the shunt
fed vertical after moving the two beverages, but saw no change in noise
levels on the West and SW beverages. I shorted out the gamm a arm to
the base. As soon as I find some boxes to put my 1:1 baluns in, I'll
install those in the rx feedlines and report back.
Thanks again to all for your helpful comments.
Dave K1WHS
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