I have one of the K5GNA modified downconverters with the corner reflector attached. Since starting to set my satellite station back up, this is one area that I hadnt addressed. I have my antennas mounted to a Channel Master rotor on a commercial TV tripod. The antennas are angled at about 25 degrees because of some ground clutter, trees, etc that I have to shoot over to get to the satellites.
With this setup, can I mount the Mode S downcoverter and have a reasonable chance at getting it to work or should I look at some type of patch antenna to get better signal picket ? Is mode S a little less unforgiving so that I have to have it more directed at the satellite than I can get away with on my current VHF/UHF antenna setup ?
Thanks,
Ron KA4KYI
----- Original Message ----- From: "Ronald Nutter" rnutter@networkref.com To: amsat-bb@amsat.org Sent: Saturday, April 05, 2008 10:02 PM Subject: [amsat-bb] AO-51 Mode S Antenna question
I have one of the K5GNA modified downconverters with the corner reflector attached. Since starting to set my satellite station back up, this is one area that I hadnt addressed. I have my antennas mounted to a Channel Master rotor on a commercial TV tripod. The antennas are angled at about 25 degrees because of some ground clutter, trees, etc that I have to shoot over to get to the satellites.
With this setup, can I mount the Mode S downcoverter and have a reasonable chance at getting it to work or should I look at some type of patch antenna to get better signal picket ? Is mode S a little less unforgiving so that I have to have it more directed at the satellite than I can get away with on my current VHF/UHF antenna setup ?
Thanks,
Ron KA4KYI
The mode S downlink on AO-51 is pretty easy to receive with a corner reflector without critical aiming: there's a video somewhere of Drew (I think...) making contacts with just such a downconverter/corner reflector combo just laying on its side on the roof of his car... The real trick is the doppler: 3x as much as on 70 cm! CAT tuning is a must.
73,
George, KA3HSW
Hi Ron!
By the way, thanks for the QSO this (Saturday, 5 April) afternoon on AO-27. I was parked SE of Flagstaff AZ, dealing with a strong wind while working that pass.
<snipped reference to K5GNA-modded S-band downconverter>
With this setup, can I mount the Mode S downcoverter and have a reasonable chance at getting it to work or should I look at some type of patch antenna to get better signal picket ? Is mode S a little less unforgiving so that I have to have it more directed at the satellite than I can get away with on my current VHF/UHF antenna setup ?
For AO-51, you can receive it easily with just the dipole and corner reflector on that downconverter. Some have replaced the dipole with a Yagi, and you could even go with some of the 2.4 GHz WiFi antennas. AO-51 is transmitting on S-band at 2 or 2.5W when it is there, so in a low orbit you should be able to hear it.
As for dealing with the Doppler at S-band, computer-control of your downlink radio is desireable. It *can* be done manually, but with the shift of around 55 kHz +/- you are adjusting the receive frequency almost all the time. When I have worked AO-51's S-band downlink, I would not have the benefit of computer control for my portable setup. I would be almost constantly adjusting the downlink frequency, but with 5 kHz tuning steps on my downlink receiver (VX-2R connected to the downconverter) I did OK.
Good luck and 73!
Patrick WD9EWK/VA7EWK http://www.wd9ewk.net/
participants (3)
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George Henry -
Patrick STODDARD (WD9EWK/VA7EWK) -
Ronald Nutter