At 05:26 AM 5/10/2008, Ronald Nutter wrote:
I have been using a 2.4 ghz Vagi antenna for my Mode S antenna the past few days. I am seeing quite a bit of signal droppout as AO-51 does a little rotating. With a circular polarized antenna do any better ? I have found a source for a 2.4ghz 10 db RHCP antenna and thought about trying that. I know I cant get it before AO-51 goes back to V/U mode but thought I could try that next time. The antenna I found has about a 50 degree pattern so I should get decent coverage since I have it pointed at a fixed elevation because I dont have an az/el rotor.
Ron KA4KYI
Ron,
From what I have read on what others are using for 2.4 GHz (mode-S) on AO-51 (or other Leo sats) a 10-dB circular pol. antenna should work fine. As far as using it without elevation control I cannot tell you how that will work. Ten dB may be a bit too narrow for best operation at all elevations. But the gain would be good to have for the period of time the satellite is within your beam. I believe Bob Bruninga has found that a fixed elevation of 20-degrees makes a good solution when not moving elevation.
If the antenna is accessible you can experiment on what angle works best by trying it at several angles.
I plan to build my self a simple corner reflector fed with a dipole which should result in about 10-dB gain. I also have an 85cm dish with helix feed that was used for AO-40. I have two 2.4 -GHz LNA's and two Drake converters (123-MHz; 435-MHz output) so that any combination will be possible when all is re-installed. I have full az-el tracking.
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