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RE: Circular patch behaves linear



Hi Patch users,
just to drop in my two cents:

I built an LHCP and an RHCP patch of the K3TZ style.. exactly to
mechanical dimensions given by K3TZ with thin metal sheet (0.3mm or 1/80
inch). 

Result: the RHCP patch showed the exactly same return loss plot as
simulated (double dip with higher frequency dip deeper) with second dip
at 2440 MHz .. 18dB return loss . At 2400MHz, it still had 13dB ret loss
with second dip at 2.3 GHz and 8dB ret. loss. so much to SWR.

Circularity: I compared AO-40 beacon strength with LHCP and RHCP patches
barefoot. Good copy (at leat for TLM, not for SSB, but enough for CW)
for RHCP, nothing at all for LHCP.. looks rather circular to me.

Conclusion: this K3TZ thing CAN be circular and quite close to the
simulated performance. I have the impression, that this could have
something to do with the thickness of the patch.. which is quite thin
for me.. any comments welcome.


Still, I will build up some W0LMD patches.. these look so much more
mechanically stable to me :-))

Any hints to get them tuned? 

DJ9PC suggested to build a signal generator with small dipole and rotate
it.. turn the tuning screw on the patch until no effect can be seen.

73s Achim, DH2VA


> 
> Message: 5
> Date: Mon, 23 Jun 2003 23:14:37 +0000
> From: "Frederick M. Spinner" <fspinner@hotmail.com>
> Subject: RE: [amsat-bb] Circular patch behaves linear
> 
> Impressive.  Those all appear to resonate a little bit high (ideally the
> center of the W in the dip should be at 2401 MHz).. but they all look like
> they'd work fine and be CP.
> 
> I never got my K3TZ style to show that dip or CP.   But I do know that
> theoretically that design should work.  I've just never gotten one to do
> that.
> 
> Congrats on that.  I probably stand corrected that the G3RUH/W0LMD style is
> the only one I've ever seen being CP.
> 
> Also all of the guys who wondered what a CP patch should look like on an
> analyzer... there you go.
> 
> Fred W0FMS
----
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