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Re: Smaller size patch



Yes, but for our applications the air dielectric is not as lossy, the patch 
is bigger and that gives more surface area (capture area) resulting in more 
gain.  Also we tend on spacing our patches at, say, 1/4 inch instead of .016 
in-- the bandwidth is like 10% instead of 1% making
tuning and reproducability better.

In commercial apps, we don't need every fraction of dB like you do for 
feeds, and therefore a patch that's 3dB off of optimum is okay, if not 
desirable because of its smaller size and reproducibility in large 
quantities.  In a feed that's 3dB of loss before the first preamp.  Not 
good.

Air patches are nasty in commercial apps because they have to be machined or 
at least stamped and assembled!

Losses in the feed is like adding noise (figure) to the receive setup.

Fred W0FMS

>From: Jon Ogden <na9d-2@speakeasy.net>
>To: "Frederick M. Spinner" <fspinner@hotmail.com>
>Subject: Re: [amsat-bb] Smaller size patch
>Date: Wed, 05 Feb 2003 12:07:42 -0600
>
>on 2/5/03 11:18 AM, Frederick M. Spinner at fspinner@hotmail.com wrote:
>
> > Actually, the gain of the patch element (and therefore beamwidth) is a
> > function of the physical area of the patch.
> > The Q (bandwidth) is also a function of the spacing-- the wider the 
>spacing
> > the more beamwidth.
> > On top of that, the dielectric adds thermal noise to the patch antenna 
>and
> > "loads" it increasing Q further.
> >
> > I'm not saying that it is impossible to use teflon for a patch.  I think 
>it
> > is and if you get a good design let us know.
>
>Most commercially made patches are teflon and not air based...
>
>????
>
>Jon
>-------------------------------------
>Jon Ogden
>NA9D (ex: KE9NA)
>
>Citizen of the People's Democratic Republik of Illinois
>
>Life Member: ARRL, NRA
>Member:  AMSAT, DXCC
>
>http://www.qsl.net/na9d   <- Updated on 1/22/03!!!
>
>"A life lived in fear is a life half lived."


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