Larry Higgins wrote:
>
> It's been very interesting reading all the postings about using shunt feed
> on 160 and 80. Apparently many of us have tried it and found that the tower
> is electrically too tall for 80.
>
> Carl, KM1H, wondered if anyone has tried an elevated feedpoint on 80 to
> solve the problem. I'm wondering the same thing. Carl, if you get some
> answers I hope you'll post a summary back here on the reflector.
>
> 73
>
> Larry, N9DX
>
Hello Larry,
Thought you might find the following of interest. It was found on
the KA9FOX web pages (highly recommended!) and offers some good
info. I have listed the URL for the article if you want to go right
to the source.
73,
Ken K4XL
http://www.qth.com/ka9fox/n4kg_antenna.txt
Subj: Re: N4KG reverse fed antenna
To: <topband@contesting.com>
Date: Wed, Nov 2, 1994 1:05 PM EDT
From: lschim@mailstorm.dot.gov
To: jholly@hposl42.cup.hp.com (Jim Hollenback)
CC: cq-contest@tgv.com
On Tue, 1 Nov 1994, Jim Hollenback wrote:
> So what is this N4KG reverse fed antenna?
>
> Jim, WA6SDM
> jholly@cup.hp.com
See article in June 1984 QST by Tom N4KG. In brief you calculate at what
point from the top of your tower represents 1/4 at the desired
frequency.
Remember to figure in top loading. At that point, connect the ground
braid
from the feedline to the tower and the center conductor to some number
of
1/4 wave radials.
In my case I have 55 ft of Rohn 25 with 8 feet of mast sticking out of
the
top. At the 55 foot level I have a KT34XA and at 63 feet a rotatable KLM
40 meter dipole. With a little help from the article (Tom estimated the
top loading of a TH6 to be about 40 feet) I guessed that My tap point on
the tower would be about 35 feet from the ground. I connected the shield
of the coax to the tower at that point, and connected four 65 foot
radials
to the center conductor and ran them out at about 55 degrees. While I
was
shooting for about 3600khz, the thing resonated at 3700khz or so, and
the
vswr at that point is 1.3:1 or so.
One of the the OH guys is using it on 160, and Tom reported that a
friend
of his did the same thing. Wonder if one could use it on 160 and 80 from
the same tower!
I've been very pleased with the results of mine. I had the tower gama
matched on 80 with about 40 radials under it. Had a recurring problem
with
water getting into the matching capacitors. Don't have that problem now.
The KG special works better than the gama matched tower, and I can mow
the
back yard again! Oh one final detail. Tom cut his for the cw band and
used a tuner to work up in the phone band. I do essentially the same
thing.
73 de Larry K7SV in Virginia - lschim@mailstorm.dot.gov
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