The SO-50 satellite is eleven years old

SO-50 satellite (Saudisat 1C) will celebrate his eleventh birthday on December 20. On board there is an FM transponder in mode J with an uplink frequency 145,850 MHz a downlikom 436,795 MHz. The difference compared to other satellites is activation CTCSS tone 67,0 Hz.

• Bandpass filters: Saudi-OSCAR 50 (also SaudiSat-1c)
• NASA catalog number: 27607
• Released: 20.December 2002
• Launcher: Dnieper (modified R-36N Voevoda ICBM (SS-18 Satan))
• Place of discharge: Baikonur
• Dimensions: a cube with a side 23 cm
• Weight: 10 kg
• Orbit: 631 x 638 km
• Inclination: 64,5 degree
• Round trip period: 97,95 minutes
• Uplink frequency: 145,850 MHz (67,0 Hz PL CTCSS tone)
• Downlink frequency: 436,795 MHz

Compared to other FM satellites, the dimensions of the SO-50 are quite striking. This is mainly reflected in the dimensions of the solar panels. So that there is no unnecessary wear on the accumulators, the designers chose to activate the transmitter with the CTCSS system. The receiver runs continuously, but a signal will appear on the downlink only in case, that the uplink signal is not only strong enough, but also with an undertone 67,0 Hz.

Miniature receiver SO-50 na 145 MHz has sensitivity -124 dBm (0,14 uV / 50 ohm) and bandwidth 15 kHz. The antenna is 1/4 vertical on top of the satellite. The audio signal is evaluated by CTCSS circuits and then passes through the NF filter to 250 mW transmitter at 436 MHz. There is also a downlink antenna 1/4 vertical. It is located on the underside of the satellite and has an inclination 45 degrees.

A two-band handheld radio with CTCSS and a two-band vertical is a minimum to work through the SO-50. Optimum are directional antennas on each band with gain 8 and more decibels, performance on 145 MHz 25W. If a dual-band station is used, a station with one connector, this system needs to be supplemented with a duplexer or a switch (in the upcoming PA, the switching of the antennas will be provided by a relay controlled by VOX).

Income is relatively difficult. Noise gate (SQUELCH) it must be open. The signal is relatively weak, in addition, it is made more difficult by the rotation of the satellite and the Doppler frequency shift. To simplify control, just set the TX frequency to 145,850 MHz and tune the signal on the downlink for the best readability.