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[Towertalk] Antenna Considerations

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Subject: [Towertalk] Antenna Considerations
From: KevNathan@DSB.WA.GOV (Nathan, Kevin)
Date: Thu, 18 Jul 2002 08:48:37 -0700
Hi All,

I first want to thank all who responded to my inquiry a couple of days ago
concerning antenna suggestions.  To those who recommended using my G5RV with
a tuner, I am already doing this with pretty good results.  The reasons I
was seeking a vertical for the WARC bands was to eliminate possible nulls I
might get off the G5RV on the higher WARC bands.  However, it seems to be a
pretty good all around antenna for those bands.

Now, to the real meat of this post.  I am going to shunt feed my tower on
160 and 80 meters.  It is 50 feet of Rohn 25G guyed with Phyllistran and
bracketed to the house at about ten feet.  It is grounded at the bottom and
I am about to tie this ground rod to the new one I put in for my failed
inverted L to which the radio system is also tied.  At the top of this tower
are a Cushcraft A3 and a 3 element 6 meter beam.

To begin with, I'm assuming I should get some rubber hose or some such
material and insulate the tower from the house bracket.  My questions
revolve around the mechanics of the shunt feed.  I am totally blind and most
of the material on the net I've found seems to be in forms I can't make a
lot of sense out of and thus it is hard to get good basic information.  For
starters, I would welcome some suggestions as to how to connect the top of
the gamma match to the tower mechanically and electrically.  Second, about
how far up the tower would be a good starting point for length of the gamma
rod/wire/whatever?  Third, about how far out from the tower would be a good
starting point?

While I don't want someone to totally design this system, I would certainly
welcome suggestions from those who may have done this in the past as to good
starting information.  Thanks much in advance for your help and 73.
Kevin, K7RX

Kevin Nathan, Independent Living Coordinator
Dept. of Services for the Blind 
3411 S. Alaska
Seattle, Wa 98118
Voice:  (206) 721-6450
Cell:  (206) 604-4767
Toll Free:  (800) 552-7103
Fax:  (206) 721-6403

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