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Re: false signals-images-harmonics-whatever? FIXED !!



Hi folks,

The alternative to a 1/4 wave open stub at 435 would be a 1/4 wave shorted
stub at 2401, right?  If so, wouldn't that be easy to build into a helix
feed?  I'm thinking of a short piece of wire parallel to the ground plane, 
with
one end attached to the feed point (N-connector), and the other end soldered 
to
the ground plane.  234/2401*12 = 1.17 inches long?

My thought here is that being a shorted stub, it would put the feed coil at 
ground
potential for most frequencies - lightning protection, 432, etc., and 
probably
do a fair job at 1.2 ghz.

Im I close?  Is there a reason to use a 1/4 open stub on 435 instead?

Greg KO6TH



>From: hasan schiers <schiers@netins.net>
>To: Jens Schmidt <j.schmidt@paradise.net.nz>, Tracy <k7kcs@attbi.com>
>CC: amsat-bb@AMSAT.Org
>Subject: Re: [amsat-bb] false signals-images-harmonics-whatever? FIXED !!
>Date: Sat, 5 Jan 2002 06:57:16 -0600
>

>From the foggy depths of my morning mind, I think it is a quarter-wave open
>stub, acting like a short circuit. At 70cm this calculates out to 5.4 
>inches,
>with a velocity factor of .80
>
>The idea is to "notch" the 435 mhz offending signal without screwing up the
>2.4 gig desired. It's a neat trick...and you can avoid cutting by using an
>1/8 wave line with a small tuning cap across the end and then tune for the
>null. (I think it was an 1/8 wave ...it's been a long time since I did it).
>


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