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Re: [TowerTalk] 75 meter antenna noise

Subject: Re: [TowerTalk] 75 meter antenna noise
From: K4SAV <>
Date: Sun, 11 May 2008 22:12:49 -0500
List-post: <">>
There are a few details missing that may affect the answer.  Is the 
noise atmospheric noise or man made.  "S9 hiss" doesn't sound like a 
description of atmospheric noise.  Are you measuring signal-to-noise on 
DX stations or local stations.  How high is the inverted vee.

A low inverted vee is a noisy antenna for DX.  A high one isn't bad.  If 
you are listening to DX on the 40 meter element of a SteppIR, my guess 
is that common mode currents are a major contributor to the signal you 
are receiving.  Same as I found out about receiving on 160 using my 
XM240.  It was better than a low dipole.  In that case the feedline was 
the real antenna , not the XM240, caused by its balun not working on 
160.  I even checked the SWR on 160 into that antenna and it was fairly 
low, which is another confirmation that the common mode currents on the 
feedline was a major contributor.  No I didn't try transmitting on it.  
So, in this case a vertical had a better signal-to-noise ratio than a 
low dipole for DX.  That should come as no surprise to those living in a 
rural area.  If you happen to live in a city, then we may be talking 
about a different kind of noise.

DC coupling the antenna should have no effect on the noise.  A double 
bazooka configured as an inverted vee should have the same signal to 
noise ratio as an inverted vee.  The double bazooka will have slightly 
less gain, but the S/N will be the same.

Atmospheric noise has been pretty bad on 80 lately due to all the 
thunderstorms.  A receiving antenna can help a lot, but when you have 
thunderstorms close by and the receiving antenna points into them, there 
isn't much more you can do.

Jerry, K4SAV

Howard R wrote:

>Can anyone recommend a way to reduce noise on my 75 meter inverted Vee or
>alternately I am looking for a quieter antenna , I am using a current fed
>balun and seems to me if I can dc couple the 2 quarter wave sections perhaps
>I can reduce the noise somewhat . Any help would be appreciated .
>When I use my folded 40 meter driven element on my Steppir for 75 meter
>receive my S/N ratio is around 40 db with my balun fed inverted Vee its
>around 15 db always have  S9 hiss .
>I was looking at a double bazooka as a replacement perhaps . Any comments.
>Howard VE2AED
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