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Re: W0LMD test results



Your axial-ratio should be better than 2 dB!  The one I built and tuned is 
probably  better than 1 db Axial ratio..  You might want to fiddle with the 
tuning screws.  If you used a 6-32 equivalent screw for the CP I'd advise 
going bigger than that.. I intentionally recommended bigger in my post 
yesterday.  In my personal experience, the 6-32 (or equiv) screw is too 
small to get enough capacatance to get the CP peaked on this patch.

If you have some method of pumping a signal into it and then measuring 
return loss, you can get it really really close to perfect CP.  I've 
desribed what to look for several times on the BB, but your looking for a 
"W" in the SWR/return loss at 2401 MHz.  Also you can adjust the second 
screw I suggested for resonance and that'll improve the performance as well.

The circularity sense is determined by the placement of the screw relative 
to the feedpoint.  If the screw is clockwise from the feedpoint as is the 
W0LMD design, the patch is LHCP for dish placements.  If you put the screw 
counterclockwise (or anti-clockwise) it'll be RHCP.

If your CP isn't tweaked (and especially if the patch is out of resonance) I 
doubt if it'll seem much better than the square patches were...

Fred W0FMS


>From: "William Leijenaar" <pe1rah@hotmail.com>
>To: amsat-bb@AMSAT.Org
>Subject: [amsat-bb] W0LMD test results
>Date: Thu, 26 Jun 2003 22:43:31 +0200
>
>Hi AMSATs,
>
>I see that I made some kind of "sandstorm" after I posted the message about 
>my test results of the previous patch haha. I am very supprised that nobody 
>else has descouvered that before, or made any notice of it.
>
>Last week I was a little busy with qrl things. I have looked for the W0LMD 
>patch information but like posted by some other amateurs I could not find 
>any detailed information.
>Today I see some message posted with some links and I downloaded the 
>drawings and after conversion to milimeters, and finding the materials I 
>made the patch like drawn :-)
>
>The patch is much better than the square patch. It is mechanical stable and 
>also more circulair :-)
>Today I did some quick circularity tests and the best results I got is a 
>2dB difference. The test was done with the patch in my hand and rotate it, 
>so not very optimal, but still much much better !!!!
>
>There is only one thing I can not find out. What is the polarisation of 
>this patch ????
>I guess its LCHP, because its designed as feed in front of a dish, but what 
>will be a RHCP design ???
>(The same confussion has been with the "square, none circulair" patch... )
>
>Does anybody know the principle of creating circularity behind this design 
>???
>Why this tuning bold is 0,5" from the feed point ??? (I would more think of 
>90 degrees to feed point)
>
>Tommorow I will wake up early and will compaire my old patch with this new 
>patch...
>Then I will find out if this design is worth its glory .-)
>
>73 de PE1RAH, William
>---
>
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