[amsat-bb] Re: Suggested mode S antennas for K5GNA downconverter

Edward Cole kl7uw at acsalaska.net
Sun Apr 13 23:36:35 PDT 2008

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 

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
>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
>of almost anything metal. An umbrella lined with aluminium foil would work
>The experts will tell you it is far from efficient however it wins on the
>easy to make and good performance stakes.
>Terry, ZL3QL.
>----- Original Message -----
>From: "Ronald Nutter" <rnutter at networkref.com>
>To: <amsat-bb at 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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