Re: [amsat-bb] Patch (K3TZ) Questions

["Frederick M. Spinner" <fspinner@xxxxxxxxxxx>]

Since the patch is at zero ohms in it's geometric center anyway, just screw 
a stud to the ground plane there.  This will not work on a "slotted 
antenna", however.

The impedance of a patch varies from about (depending on design) from 200 
Ohms on the periphery to zero ohms in the center.  The 50 ohm point is 
somewhere about halfway between and this is why the feeds are in a little 
from the edges.

Fred W0FMS

>From: "Bill Acito" <w1pa@hotmail.com>
>To: <amsat-bb@AMSAT.Org>
>Subject: [amsat-bb] Patch (K3TZ) Questions
>Date: Mon, 1 Jul 2002 15:16:37 -0400
>
>1) Has anyone tried leaving the corners and putting a slot in the K3TZ 
>patch
>design to ensure circular polarization? There seemed to be some discussion
>(from K3TZ himself, no less) that the design is not c-polarized (although,
>from what I've read, folks are getting good performance anyway). Has anyone
>tried this design:
>
>http://nr.stic.gov.tw/ejournal/ProceedingA/v24n2/130-133.pdf
>
>...to see if this improves performance? I assume the scaled up dimensions
>are way off because of the difference in dielectric constants between the 
>pc
>board material in the paper and air. I even found references that K3TZ's
>design _should_ be circular polarized:
>
>http://www.eetasia.com/ARTICLES/2001JUN/2001JUN15_RFD_AN.PDF
>
>but I am no patch design expert by any stretch of the imagination.
>
>2. G3RUH's patch is a grounded design (per his literature), to prevent
>static damage to the front end. Again, I'm no expert, but is there any
>reason why a 100K-1Mohm 1/8w resister couldn't be used as a standoff for 
>the
>K3TZ design patch, providing a discharge path from the patch element?
>
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>
>Bill
>W1PA
>
>----
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