[amsat-bb] VO-52 - OK to Work in FM?
clintbradford at mac.com
Fri Jun 11 18:41:37 PDT 2010
The Bengal ham club posted about five years ago instructions for working V)-52 in FM mode. Is that still OK to do?
"HAMSAT or VO-52 is a satellite intended for SSB/CW operation. However as in VU land very few of us can afford multimode VHF/UHF radios we are accessing Hamsat on FM for which it is best to stick to the centre frequencies (435.250 uplink and 145.900 downlink). It is also best to simultaneously monitor your own signals on the downlink using a separate radio. Hamsat requires around 100 watt ERP for solid 59 signals. So if you are using 10 watts RF the recommended antenna gain is around 10 db. However Hamsat or VO-52 have been accessed on high elevation passes using 25 watts ERP. If you want to use omni directional antennas you can build a turnstile or an eggbeater antenna which has a dome shaped radiation pattern with circular polarisation. Separate 10 element UHF and 5 element VHF crossed yagis with circular polarisation would give excellent results. Only keep the transmission line loss (particularly on UHF) minimum. Use hardline CATV cable if transmission line is more than 100 feet. Otherwise if you use RG-213 keep the feeder length to around 20 - 30 feet. I have been using a handheld arrow yagi antenna with RG-58U cable of around 1 meter length. Doppler compensation is needed particularly on the UHF uplink where the signal will shift around 10 KHz. So for the uplink it is best to start from 435.240 MHz during AOS and end at 435.260 MHz at LOS and on the downlink start receiving 5 KHz up at 145.905 MHz and end at 145.895 MHz. Currently the VU transponder is on and it has a beacon (continuous carrier) on 145.936 MHz though we have not yet received the beacon from Calcutta / Kolkata."
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