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Re: Suggested mode S antennas for K5GNA downconverter



For AO-51 not much gain is needed so why not place it in front of a 
corner reflector?  The ground-plane of the patch should not be 
modified as it affects the feed impedance.  There used to be a corner 
reflector design in the ARRL Antenna Book.  Spacing in front of the 
corner also affects impedance.  If I remember correctly a corner 
reflector using a dipole feed has about 9-10 dB gain.  A 2-foot dish 
would be around 22-dB and much more difficult to track due to the 
narrower beamwidth.  10-dB is quite forgiving which would be useful 
for the rapid tracking rates of a Leo satellite.  A dish will be 
needed only when we get the next Heo with its much higher orbit.

If not mistaken, the patch has a gain of about 9-dB so may be 
sufficient by itself!

When I get my satellite antennas re-installed (this spring), I plan 
on having both a 33-inch dish with helix feed (my old AO-40 setup) 
and a corner reflector with two separate preamps and Drake 
converters.  Added to this will be 144 and 432 circular polarity 
x-yagis and a 1268-MHz Loop yagi for mode-L.  Most of this will be 
overkill until the next Heo.  You can see my plans at 
http://www.kl7uw.com/sat.htm

Thanks for the easy patch design.  I'll have to make one up for 
comparison with the helix feed.

73 Ed - KL7UW

At 06:26 PM 4/13/2008, Terry Carrell wrote:
>Try this patch - its very easy to make, I used some scrap brass, and works
>very well. It is circularly polarised although for correct sense it is
>designed for
>reflection use, i.e., with a dish
>
>http://www.kiwisat.org/23cm_patch.pdf
>
>It was used to receive AO-40  direct and is currently in service in a 600mm
>dish. Gain can be increased by using a "V" or parabolic shaped reflector
>made
>of almost anything metal. An umbrella lined with aluminium foil would work
>fine.
>
>The experts will tell you it is far from efficient however it wins on the
>simplistic,
>easy to make and good performance stakes.
>
>Terry, ZL3QL.
>
>----- Original Message -----
>From: "Ronald Nutter" <rnutter@networkref.com>
>To: <amsat-bb@AMSAT.Org>
>Sent: Monday, April 14, 2008 11:02 AM
>Subject: [amsat-bb] Suggested mode S antennas for K5GNA downconverter
>
>
> >I am trying to come up with a portable sat station that can fit in a
> > briefcase.  I have the dipole and reflector antenna that K5GNA sells for
> > his downconverter but I am looking for something compact that can fit in
> > the briefcase and the reflector cant.  I have thought about the G3RUH
> > patch antenna but that is a little pricey for me at this point.  Are
> > there any other antennas that someone can suggest that I try for this
> > quest ?
> >
> > Thanks,
> > Ron
> > KA4KYI
> > _______________________________________________
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