[TowerTalk] beam antenna patterns; groundwave

[Don Havlicek]

How, pray tell, did you calculate 6 db f/b on a VERTICAL? ... Did you 
rotate it?   Any WHY?
Don
N8DE

Jim Jarvis wrote:
> 
> Folks,
> 
> While I agree with Tom, in theory, that all manner of localized
> effects can come into play, mapping pattern using groundwave at
> far-field has SOME value.   I did it routinely in Vermont, with a
> station 5 miles away.  We had hills and trees in between.  What came
> back was quite close to claimed specification.
> 
> To be sure, the groundwave pattern isn't the same as that at real arrival
> angles.  But it allowed me to estimate f/b on both an lpda and a steppIR,
> and to do it against a co-located vertical antenna.  The vertical was used
> as a frame of reference.   The technique also allowed me to properly
> decouple
> the feedlines.  When we first started, I had a 6dB f/b on my vertical!
> Adding common mode chokes and running the coax down separate tower legs
> tamed that beast.
> 
> 
> n2ea
> jimjarvis at ieee.org
> 
> 
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