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RE: To all "patchheads"...



Yeah, that is the article that gave me the idea.  There are two reasons why 
I think the screws might be better:

1. I really, really like to have my downconverters grounded.  It's really 
convienient both from this grounding standpoint, and also a mechanical 
standpoint to use a small (#2 or #4) post to support the patch at the 
center. (If in the geometric center, Z=0 Ohms anyway) This obviously could 
affect the patch with the slot in it.

2. The copper tape idea is appealing, but so is a couple of small screws to 
tune the patch.  What I mean by this is:  I use a brake shear here at work 
to cut the patches to resonance.  It's very easy to go too far as a 1/16" 
cutoff is 5-10 MHz.  If I can adjust the resonance with both sets of screws, 
then back off on the appropriate one, I can tune a slightly undersized 
patch.  This way my precision of the shearing doesn't have to be +/- 0.5 
mm....

However, the aluminum tape idea is fantastic..  The slot patch I tried 
showed some signs of the "dip" that was in that article because of the dual 
resonances.  Unfortunately it was pretty hard to tune both of the "dips" at 
the same time.  This is what I'd like to alleviate by using the tuning 
screws.  I'll let the group know how it goes once I get the PEM nuts I need 
for tuning.

By the way, as PATCH16 always calculates the 2.401 GHz square patches to be 
around 2.25 inches, I find that 2.05 inches consistantly is closer in 
reality with a 1/8" spacing...  I think PATCH16 falls apart at spacings much 
larger than circuit board...

Fred W0FMS

>From: "Tom Clark \(W3IWI\)" <w3iwi@toad.net>
>To: "'Frederick M. Spinner'" <fspinner@hotmail.com>, <amsat-bb@AMSAT.Org>
>Subject: RE: [amsat-bb] To all "patchheads"...
>Date: Mon, 3 Jun 2002 20:57:06 -0400
>
>Fred
>
> > [snip] I am wondering if it'd be
> > possible to CP a (truly) square patch if a couple of
> > capactive tuning screws
> > were located 90 degrees apart (on the flat sides) on a
> > slightly higher than
> > resonant patch that was fed at 45 degrees (on the diagonal)?
>
>There is a simple and elegant solution that doesn't use tuning screws -- it
>uses a tuning slot thru the middle. For details on a 1900 MHz antennas, 
>take
>a look at the paper by LU and YANG:
>    http://nr.stic.gov.tw/ejournal/ProceedingA/v24n2/130-133.pdf.
>
>They indicate the slot size is critical. An oversize slot could easily be
>trimmed to length using conductive (copper or aluminum) tape. Copper foil
>tape can be found at your local store that services artists who make 
>mosaics
>using colored glass since they can solder to the copper. Aluminum tape can
>be found at hardware stores for sealing air conditioning ductwork.
>
>73, Tom
>
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