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[TowerTalk] Antenna Problem - Solved

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Subject: [TowerTalk] Antenna Problem - Solved
From: (Dick Flanagan)
Date: Sun, 14 Jun 1998 15:23:56 -0700
A little over two weeks ago I wrote:

>Okay, here's where I could really use some help, fellas....
>As some of you know, I finally got my antennas hung this past weekend.  The
>arrangement is:
>  Hy-Gain TH-11DX 11-element 10-12-15-17-20M yagi 1 ft above tower
>  M2 6M7 7-element 6M yagi 6.5 ft above tower
>  Cushcraft 40-2CD 2-element 40M yagi 13 ft above tower
>The TH-11 was tuned for phone.
>The 40-2CD was tuned for "high CW."
>With the tower raised to 72 feet, all bands show good VSWR =except= both 12
>and 40 are unacceptably high (2.8:1).  Both bands dip to minimum SWR where
>they are expected to, but that SWR is simply too high.
>The TH-11 and 40-2CD are connected to a common feedline via an Ameritron
>coax switch that -grounds- the unused antenna.
>With a minimum 10 ft separation between the TH-11 and 40-2CD, the
>Conventional Wisdom said there would not be any significant interaction.
>Me thinks I am seeing an interaction.
>Any thoughts?  Words of wisdom?  Words of condolence?!  :)

I received over a dozen helpfull and knowledgable responses, but only one
actually came close to identifying the culpret.  Dave Hachadorian, K6LL,
asked a very basic question:

   Are you using one of those antenna analyzers for your
   swr measurements? Try a conventional swr bridge.

I was, indeed, using an MFJ analyzer and once I replaced it with a
conventional transceiver/bridge combination, I was blessed with
picture-perfect SWR curves on all bands!

Thanks to all for their help and I apologize for not being more careful in
my measurements before going to the net for help.

73, Dick

Dick Flanagan W6OLD CFII Minden, Nevada DM09db (South of Reno)

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