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[TowerTalk] TH11 and Shorty 40, Revisited

To: <towertalk@contesting.com>
Subject: [TowerTalk] TH11 and Shorty 40, Revisited
From: n4kg@juno.com (T A RUSSELL)
Date: Tue, 3 Aug 1999 05:59:21 -0600
On Mon, 2 Aug 1999 23:34:16 -0500 "Phil Clements" <philk5pc@tyler.net>
writes:

SNIP

The bad thing about the interaction is you do not know 
what kind of pattern skewing is happening on 40 m also.

SNIP

K5PC
.........................

It is highly unlikely that any high band elements will affect 40M
performance
when the booms of the high band antenna and 40M beam are parallel.
This is due to the fact that all high band elements are less than 50% of
a
half wavelength on 40M.

If the booms are rotated 90 degrees to each other, it is quite possible
for
the tribander boom, end loaded by 20M elements, to interact with the 40M
beam since a 24 ft boom end loaded by 20M elements is self resonant
at approximately 7.5 MHz ( I arrived at this conclusion after measuring 
the self resonant frequency of an exact half scale 10M beam on a 12 ft 
boom which grid dipped at 15 MHz.)

de  Tom  N4KG

re:  increased SWR on 17M, the simplest solution is to just live with it.
Either use a tuner to get a better match, or just tune for maximum 
power output.  A 2:1 SWR isn't going to reduce efficiency by a
significant
amount.


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