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Re: [TenTec] ant

To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Subject: Re: [TenTec] ant
From: "Paul Christensen" <w9ac@arrl.net>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Fri, 14 Jan 2011 11:52:15 -0500
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
> The link and the output coil do the balancing, I don't force
balance by grounding the center of the output coil, though that often works.

The grounding of the antenna side of the coil (typically between two caps 
connected in series, with the the opposite end of the caps connected across 
the ends of the coil) as seen in many link-coupled tuners has me baffled. 
The EF Johsnon transmatch also uses a ground tap, but the output caps are 
configured to create a voltage divider.  I have looked for an explanation in 
old versions of the ARRL Antenna Book as well as the Frank Jones Antenna 
Books from the late 1930s.  Cebik discusses it briefly but only in the 
context that "it is optional."  It seems to me that the tap should stay 
ungrounded with balanced feeders  With the center grounded, it also seems 
that it creates a greater opportunity for unbalance.  By removing the ground 
tap, doesn't that provide the best opportunity to force equal current into 
the line, while also keeping line current perfectly anti-phase?

> Then I tap the feed line to the turns where it matches. And use a
variable link instead of the series capacitor on a fixed link.

I have seen this done to improve current balance, but what is the mechanism 
by virtue of the grounded tap that assists with keeping line current 

Paul, W9AC 

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