[Antennaware] center loading versus ground loading

Gary K9GS garyk9gs at wi.rr.com
Sun Jan 31 11:41:21 PST 2010

I have been contemplating an antenna design to cover 40, 80, 160M. 
Basically ~32 ft of aluminum tubing/mast, a trap, then more tubing/mast to 
~60 ft (possibly using a capacity hat to tune on 80M) and then a second trap 
above the capacity hat with a T-top loading wire to tune on 160M.  My goal 
would be no switching/control lines at the antenna.  I work almost 
exclusively CW so I don't need to cover the entire 80/160M band.



Gary K9GS
Gary Schwartz           email: k9gs (at) arrl.net
Check out K9NS on the web: http://www.k9ns.com
Society of Midwest Contesters (SMC)     http://www.w9smc.com/
GMDXA http://www.GMDXA.org

----- Original Message ----- 
From: "Art Trampler" <atrampler at att.net>
To: <antennaware at contesting.com>
Sent: Friday, January 29, 2010 10:48 PM
Subject: [Antennaware] center loading versus ground loading

I live on a fairly small lot and use a Hy-Gain AV640 for 40 through 10 and
currently have no antenna for 80 or 160.

My backyard is about 90 x 70 but has some ill-placed and ill-shaped trees
for either wire antennas or a tower.

So I am thinking of another vertical, but this one ¼ wave with a radial
field.  I would like to get 80 and 160 out of it.  I don't mind having to
guy it, or even having to pour a concrete base for it.

My first thought is to use aluminum irrigation pipe as others have, and have
about 60 to 65 feet of it, an insulator and inductor and high voltage relay,
and then perhaps 15 to 20 of much smaller aluminum tubing, with a sloping
capacity hat of four wires going partially down the four top guys.  I don't
know if I could get away from the relay, and put up a trap instead but am
wary of using a true trap (coil & capacitor) rather than just a large, high
Q coil.

As you can see this idea is full of possibilities and mechanical drawbacks,
so the question is, is there that much to gain from the center-loaded design
with capacity hat, versus a switchable tuning network at the base of the

Your input is appreciated.  I am hoping to make this a summer project and
reward myself with 80 and 160 in the winter.



Art Trampler, KØRO

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