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[TowerTalk] QUAD : coax switching and 40m..

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Subject: [TowerTalk] QUAD : coax switching and 40m..
From: (Paul Ferguson)
Date: Tue, 8 Jul 1997 11:27:45 -0400
> Recently I replaced my Mosley PRO67B by a 3 element 5 band quad.It
> will = be mounted in box configuration at 55ft and fed with
> separate1/4 = wavelength 75 ohm coaxlines thru a remote coaxswitch..
>     (a) What would be preferred : unused ports switched to ground or
>     (b) isolated ?

I modelled a two-element 5-band quad with each element fed with 1/4
wavelength 75 ohm coax to a switchbox. An EZNEC model showed a bad
affect on performance when the unused 1/4 wavelength lines were
shorted at the switchbox. When the unused lines were left open at the
switchbox, there was little interaction with the unused elements.

My EZNEC model included the 1/4 wavelength lines in the model. I think
you would see the same performance degradation if you model the
antenna without the 1/4 wave lines and leave the unused driven
elements open.

I did model a few cases of random length fed lines to the switchbox,
and I did not see any significant performance degradation when the
unused lines were shorted.


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