I'd agree with Chuck and Jim: a 20-degree squint from a correctly
constructed T-match just isn't possible. To produce a squint of that
magnitude, something at the feedpoint would need to be grossly wrong
(something like one side of the driven element being disconnected
completely).
It seems much more likely that N6BT found a batch of antennas that had
been wrongly constructed. If he had corrected those errors and retained
the original T-matches, the antennas would have worked 'as designed'.
I haven't found any evidence of squint from a gamma match either... but
what I *have* found on 6m was elevated receiver noise, which disappeared
when I changed to a center-fed driven element with a choke balun.
With and today's understanding about unwanted common-mode currents, and
ever-increasing levels of RF noise all around us, I no longer use any
matching method that directly connects the driven element to the boom.
73 from Ian GM3SEK
>-----Original Message-----
>From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
>Chuck Smallhouse
>Sent: 28 February 2015 04:34
>To: towertalk@contesting.com
>Subject: [TowerTalk] T Matches
>
>
>## He also mentioned about HF yagis using the T match...and the
>200:50 ohm coax balun. Several of them had the main lobe
>canted off to one side by 20 degs ! The fix was to replace the T
>match with a conventional hairpin setup. He did not mention the
>brand, but I suspect it was telrex... the only co I know of that used
>a T match. Why the lobe ended up skewed 20 degs to one
>side is beyond me. He mentions fixing several of them.
>
>I have very successfully used T matched VHF/UHF high gain yagis from
>venders such as Telerex, KLM, M2, K1FO and others and have never
>experienced any offset of their patterns. They all used a 1/2 W/L
>coaxial "balun" as a 50/200 ohm matching device. In fact I've never
>even detected offset of the main lobe on Gamma matched yagis, as some
>have rumored to have experienced.
>
>Proof of this observation, is the receiving of moon echoes of arrays
>of 4, 6 or 8 T matched yagis . The echoes, sometimes quite weak,
>where heard when the arrays were optically pointing at the moon.
>
>I have not read N6BT's book, I so don't know how he determined or how
>he corrected the perceived 20 degree offsets of the T matched yagis .
>
>W7CS
>
>
>
>
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