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[TowerTalk] Measuring beam forward gain.

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Subject: [TowerTalk] Measuring beam forward gain.
From: "Jim Thomson" <>
Date: Thu, 31 Dec 2009 05:02:06 -0800
List-post: <">>
Al Williams wrote:
> What errors may be caused by:
> The signal generator being too close (or too far away) --how far away is ok?
> The signal generator being too low in height?
> Although antenna modeling programs will display a 3d gain pattern, it seems 
> difficult to me to quantify the gain.  Thus one uses an azimuth gain pattern 
> for specific elevation angles. Can the rotational gain difference change for 
> different elevation angles?
> k7puc

I only use these measurements to measure relative gain between
two different antenna configurations.  Measuring absolute gain
is a whole nuther ball of wax.  For my measurements, I put the
sig gen 1000 feet away.  That is many wavelengths, even on 40 meters.
It is 30 feet high, which is adequate, even on 40 meters.
I suspect you could get away with much less distance and height,
but I haven't tried it.  I feel confident that whatever maximizes
the gain on the range will maximize gain at all useful takeoff
angles during actual use.

Rick N6RK
  ##  and what kind of  ant is supposed to be used on the sig gen ??    
 What if the gain of the signal gen ant is NOT flat across the band ?? 
I wouldn't   use a vertical or similar.  

##  perhaps  one of my local ham friends.. aprx  2 kms  away could
feed me a constant cxr.   And yes,  I'm  familiar with using hp test
sets to measure down to .1 db , when  driven by RX audio from the
xcvr [ in my case, from some rx audio rack gear]   You are correct,
agc is shut off.. and rf gain reduced, and padding inserted.
Being able to plot db  vs  0-360 deg on a pc is a new one for me.

Tnx........... Jim   VE7RF 



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