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Re: [TowerTalk] beam antenna patterns; groundwave

To: jimjarvis@ieee.org
Subject: Re: [TowerTalk] beam antenna patterns; groundwave
From: Don Havlicek <n8de@thepoint.net>
Reply-to: n8de@thepoint.net
Date: Sat, 26 Jun 2004 14:31:44 -0500
List-post: <mailto:towertalk@contesting.com>
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@ieee.org


_______________________________________________


See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.

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_______________________________________________

See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.

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