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[TowerTalk] Nosey noise question

Subject: [TowerTalk] Nosey noise question
From: K4SAV <>
Date: Sat, 28 Jan 2006 12:25:30 -0600
List-post: <>
I have a temporary low inverted vee for 160 meters. The apex is at 50 ft 
ant the ends are at 15 feet. It has a choke on the feedline. Yes, I know 
it's a lousy DX antenna. I also have an XM240, 2 element 40 meter beam 
at 65 feet. The inverted vee is under the beam. On receive on 160 meters 
the 40 meter beam has a much better signal to noise ratio on ALL 
signals. My question is WHY?

The noise in question is atmospheric noise. I'm not considering TV 
birdies and electric fence noise. The 40 meter beam has a little 
directivity on 160 meters but it is better than the inv vee no matter 
where it is pointed. I looked at the EZNEC response of these antennas to 
see if I could answer the question, but the answer wasn't there, or if 
it was, I sure missed it.  The patterns of both of these antennas are 
close to the same. Looking at the patterns, you would expect the 
inverted vee to be little lower noise if the beam was pointed the wrong 
direction, but this isn't the case. The gain on the 40 meter beam is 
about 12 dB below that of the inv vee. That's mainly because of the 
large coax loss due to the huge SWR. And no, the signal to noise ratio 
does not change if I add attenuation when using the inverted vee.

So, any of you low band noise gurus care to venture a guess why? I 
always had the impression that the only way to improve signal to noise 
ratio on 160 was to narrow the receive lobe pattern.  Am I missing 
something? There has to be a logical explaination for this.

Here is another piece of (maybe unrelated) data. Yesterday I went out 
and quickly put out a 1000 ft BOG (unterminated) for the 160 meter 
test.  It had a ground and a common mode choke on the feedline. It 
didn't work.  It was noisier than either of the other two antennas.  
Shortened it to 700 ft, and still no good. Didn't use it. This was 
puzzling also, but not as much as the beam/inv vee question.

Jerry, K4SAV

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