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Re: [TowerTalk] Fwd: Adjusting a Gamma Match on a Yagi with an AntennaAn

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Fwd: Adjusting a Gamma Match on a Yagi with an AntennaAnalyzer
From: Bob Alexander <realex@flash.net>
Date: Wed, 10 Nov 2010 07:08:41 -0500
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
On 11/9/2010 9:38 PM, n8de@thepoint.net wrote:
> The gamma match itself is an inductor ... you can only cancel that
> inductance by putting a series capacitor inline with it.  IF you do
> not, changing the length of the driven element will change the
> APPARENT impedance, but it will still have an inductive (reactive)
> component.
>
> 73
> Don
> N8DE
>
I have a couple of homebrew 4 el on 3/4 wavelength boom yagis  with 
gamma matches.  The antennas were designed to have a -j component at the 
feedpoint.  Using a gamma match without a capacitor resulted in a 
slightly inductive feedpoint impedance.  After shortening each end of 
the DE a  25 dB return loss was measured at the design frequency.   No 
inductive component.
73, Bob, W5AH
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