Saudisat 1C or SO-50, Saudi-OSCAR 50

Saudisat 1C or SO-50, Saudi-OSCAR 50

Saudisat 1C or SO-50, Saudi-OSCAR 50 is an FM satellite available for Amateur Radio operators. It has also experiments other than the amateur radio transponder. It is a low earth orbit satellite (LEO) with a period of 97.5 minutes, which was launched in December 2002. The uplink frequency is 145.850 MHz and downlink frequency 436.795 MHz. So it is a V/U satellite. PL tone (CTCSS) for the uplink is 67.0 Hz. But there is a ten minute timer which has to be armed by an initial carrier with PL tone of 74.4 Hz. Once armed, other users need not use the PL tone of 74.4 Hz and the transponder will continue working. PL means “Private Line” as per Motorola’s terminology as it is a tone squelch. Sending the 74.4 Hz tone again within the ten minute window will reset the ten minute timer.

Receiving antenna of SO-50 is a quarter wave vertical antenna mounted on the top and the transmitting antenna is another quarter wave mounted on the bottom of the satellite. Initial rated power output was 250 mW, though some say that the current output is as low as 50 mW. The receiver has a sensitivity of -124dBm. SO-50 has a footprint which includes VU land. The satellite weighs 10 kg and has been designated as a Microsatellite by AMSAT. There are also reports that downlink is sometimes 5 kHz lower. Today VU2AAP heard my CQ call on SO-50 and replied, but I could not hear him, in the first pass which I tried. In the second pass after about one and a half hours, I could hear VU2AAP calling CQ faintly, but distinctly. My reply did not reach him well. He also heard someone calling faintly. So I have to improve my setup for SO-50. One limitation was that the websites which I had used for Doppler tracking were down and it was a ‘blind’ Doppler tracking.