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[TowerTalk] Re: T-Match versus Gamma Match

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Subject: [TowerTalk] Re: T-Match versus Gamma Match
From: (Martin Ellis)
Date: Wed, 09 Jul 1997 19:32:18 +1200
> Question:  Is the T-match juggling of length parameters REALLY
> simpler than the Gamma match juggling? 

Hi Terry,

Also please consider:
1. The T- match is feeding both sides of driven element-
said to improve pattern, particularly where yagis are in close
2. The half-wave 4:1 coax balun avoids the need for a choke balun,
and allows the sliders to be set at the 200 ohm feed point.  This 
gets the sliders well away from the boom.  Perhaps this is important 
for yagis which have a low feed impedance.
3. I think the extra length is a one-time compensation, leaving the 
sliders as the tuning adjustment.
4. The gamma without a capacitor is said to give the antenna a
reduced bandwidth.  The half-wave balun is said to improve bandwidth.
5. In the special case when the sliders are extended to the ends
of the driven element, the T-match resembles a folded dipole,
which has a nominal feed impedance of 300 ohms.
6. The simplified T-match is used commercially by M2 and on some
C/C products - not sure about any others.     

Martin ZL1ANJ

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