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" [email protected] To: [email protected] 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 _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
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