All:
The variation in SWR during QRO operation with certain autotune amps is
the main issue with open sleeve-fed Yagis. In an earlier posting I
mentioned (tongue in cheek) that Bencher developed a solution for their
Skyhawk tribander: spacers and non-conductive collars with set-screws to fix
said spacers in place on all three DEs. "Bencher" (that's how the e-mail
was signed) confirmed that, indeed, the Alpha autotune amp (model not
identified) had a tendency to chace after the varying SWR.
Also, Steve K3SA (SK) likewise confirmed to me that he had experienced
exactly these symptoms while running his Alpha at 1.5 kW. He said he
reduced power to 1.2 kW and the Alpha was happy.
Granted, I have no first-hand experience with this phenomenon, and I
pass on this info about Skyhawks FWIW. However, I DO have a Skyhawk which
is awaiting its tower, and I DO have the spacers which will be installed -
QRO or not.
73 de
Gene Smar AD3F
-----Original Message-----
From: n4kg@juno.com <n4kg@juno.com>
To: TOWERTALK@contesting.com <TOWERTALK@contesting.com>
To: <towertalk@contesting.com>
Date: Wednesday, May 16, 2001 9:52 PM
Subject: Re: [TowerTalk] Force 12 C3 spacers
>On Wed, 16 May 2001 K7LXC@aol.com writes:
>>
>> Remember that the only antenna parameter hams can measure is SWR so
>> some of us tend to become relatively anal about *low* swr so anything
>that
>> upsets it - no matter how minor - is viewed with some concern.
>>
>> Cheers, Steve K7LXC
>> Tower Tech
>>
>
>AMEN Steve !
>
>Allow me to give you a couple of examples of high SWR antenna
>performance.
>
>#1 After a 30 minute ragchew and some persuasion, I convinced
>an African station I was working on 15M to try 17 and then 12 M
>with his 15M dipole. He had a great signal on 17M, tuning the
>pi-network of this TS-830 for maximum forward power. We then
>tried 12M (WAY past his usual bedtime) and again made contact.
>He was so excited he asked if I thought the 15M dipole would work
>on 30M where it was only half size. I was more than game so again
>we QSYed and made contact. He stayed on 30M for another hour
>handing out the first 30M contacts (as far as I knew) to several
>European and North American callers.
>
>#2 My 160M elevated GP also supports one end of my EU / S.Pac.
>80M dipole and has an 80M inverted vee on a pulley for JA / SA.
>During the winter months I like to have my 80M inverted Vee
>available for the SE Asian openings at Sunrise and Sunset.
>Yes, it severely detunes the 160M GP. I just tune for maximum
>forward power (1400W) and accept the high 'reflected' power (400W).
>It didn't seem to hurt me when I worked the ZD9, ZL9, and XZ
>DXpeditions.
>
>Bottom Line:
>
>An antenna does NOT need to be resonant (or matched)
>to radiate. As long as Nothing ARCs and Nothing MELTS,
>NO HARM DONE, at least with 3-500 glass tubes.
>
>de Tom N4KG
>
>
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