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[TowerTalk] Operators needed for CQ WW CW; Gamma Match vs T-Match

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Subject: [TowerTalk] Operators needed for CQ WW CW; Gamma Match vs T-Match
From: (Frank Donovan)
Date: Sat, 22 Nov 1997 11:51:45 -0500 (EST)
Hi Tom!

Too bad u can't make it for CQ WW CW.  Due to unexpected conflicts that
occurred with several of our operators, we still need several experienced
operators for next weekend.  If anyone else would like to join the 'LPL
Team next weekend, drop me a line at:

Tom, perhaps u would like to join us for ARRL?  80M is a blast from here
with four 2 element quads at 170 feet and eight Beverages.

Regarding the gamma match, I abandonded it mainly because of two
significant disadvantages associated with the gamma matching capacitor.

- The gamma matching capacitor is a reactance in series with each
phasing line in a stacked Yagi array.  Rather than forcing this value to
be exactly identical for each Yagi (and moisture can subsequently change
their values), I preferred to eliminate the capacitor entirely by using a
T match design that requires no capacitors at all.

- A fairly high voltage appears across the gamma capacitor, which makes it
susceptible to voltage breakdown, especially when moisture is present.
I prefer to eliminate this failure mechanism entirely.

I also made the tradeoff in favor of a T-match vs a split driven element
for similar reliability reasons because of potential failures that might
occur in baluns required for split driven elements.  The 4:1 coaxial balun
used in the T-match is nearly bulletproof (I've never had a failure...).
However, the split-driven element offers significant performance
advantages in a phased Yagi array that might lead to re-consideration of
this trade...


On Sat, 22 Nov 1997, T A RUSSELL wrote:

> What don't you like about Gamma matches?
> Would dearly love to drop by next weekend but this year is just not
> in the cards.
> 73,  Tom  N4KG

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