I have a Kenwood TM-V71A dual-band radio that I have attempted to use to listen to the FM repeater on the SO-50 satellite. I'm using a home-made dual-band yagi antenna made out of coat hangers, that I built from these instructions: http://www.amateurradio.bz/4_dollar_satellite_antenna.html
I tested out the antenna by listening to some local repeaters and weather frequencies and it seems to work fine for that. I double-checked that I'm using the right downlink frequency for the satellite, and that I have the correct time and direction info from pass predictions obtained here: http://www.amsat.org/amsat-new/tools/predict/index.php
I haven't even bothered trying to transmit yet, because I can barely get a receive signal from SO-50. When I attempt to listen to a satellite pass, at approximately the halfway point where the satellite is at maximum elevation, I can hear a clear signal for about 5-10 seconds, and then nothing for the rest of the pass. This has happened several times now. On passes with low elevation (less than 20 degrees from horizon), I hear nothing at all. On passes with high elevation (45-70 degrees from horizon), I will get a few seconds of signal, right around the middle of the pass.
So what am I doing wrong? I'm pretty sure I've built the antenna correctly, and have the correct pass times. I started out using the directional information, but now I basically just spin in circles at all different angles, trying to get any signal whatsoever. I also rotate the antenna for different polarizations. The times that I do get a few seconds of signal, it may end up being from the totally wrong direction than what the pass prediction said.
Do I need to be at a much higher elevation than ground-level in my back yard? What else could be going wrong? Are there other satellites that I can try? It seems to me that SO-50 is the only operational FM voice repeater (aside from the ISS, which isn't always in voice mode, if I understand correctly).
Thank you for any help.
EDIT: I had been adjusting for Doppler shift at first, but then left it at the centre frequency, as it did not seem to be making a difference. However, the chart provided by Pete NU9W was very helpful in making me realize the problem. I think my radio isn't sensitive enough to adjust for Doppler shift properly. It will only change the frequency by 25 kHz at a time, and the chart suggests adjusting by 5 kHz at a time. In my case, I can be 5 kHz off centre, or 30 kHz off in either direction. Since 30 kHz is too far off, it would explain why I only hear something in the middle of the pass.
EDIT 2: I figured out how to change the step frequency on my radio to 5 kHz instead of 25 kHz. I will try using this setting and see if I can adjust for Doppler shift better next time.