Satellites

Andy started his talk by giving the meeting a brief history of satellites starting with Sputnik 1 which was launched 4th October 1957 by Russia. Sputnik 1’s launch was of great concern to the USA because it meant that Russia had the capability to attack, with a missile, any part of the USA no matter where in the world.
It took the Americans 4 months to catch up; on the 31st January 1958 Explorer 1 was successfully launched.

Radio Amateurs did not want to be left out of the space race, on the 12th December 1961 OSCAR 1 was launched quickly followed by OSCAR 2. Both these satellites were no more than battery powered beacons and after a few days the batteries became exhausted. But many radio amateurs successfully received them.

OSCAR 3 was the first true amateur communications satellite with a transponder and solar cells to recharge the batteries, since then there has been literally 100’s of amateur satellites launched and they have become truly international projects, bringing together radio amateurs, universities and schools.

Andy went on to explain that OSCAR was an acronym which stood for Orbiting Satellite Carrying Amateur Radio. And that Amsat were the organisation which designed, planed, built, launched and supported amateur radio satellites world wide. Amsat UK look after UK interests and their Web site can be found at http;//amsat-uk.org/.

We then looked at the different types of orbits;

LEO Low Earth Orbit – Most amateur satellites and the international Space Station are in Low Earth Orbit, overhead passes can last for between 10 and 20 minutes.

Geostationary – Used mostly for commercial communication satellites such as TV it takes 24 hours to complete one earth orbit so the satellite appears to stay stationary.

HEO High Earth Orbit – Elliptical, an elliptical orbit means that the satellite can be visible for many hours allowing many QSO’s.

Next we looked at satellite tracking using either on line Web based trackers or tracking programs and the importance of keeping the latter’s kepler elements up to date.

Andy then explained the way that the satellite travels through space causes the transmitter and receiver frequencies to change, known as Doppler shift and how to compensate for this during the pass.

He then when on to look at Cubesats and satellite architecture, how FM cross band repeaters work and inverting linear transponders. Next we looked at the sort of radio equipment a beginner could use to make their first contact through a satellite carrying a FM cross band repeater.

All that is needed is a hand held transceiver a 2m / 70cm beam such as the Arrow Antennas beam and the use of a diplexer to split one antenna feed in two radios or one radio into two antennas (also a good way to stop de-sense).

Finally we looked at using the Amsat Status List to identify a suitable satellite ready for that first QSO.

The talk finished with a you-tube video of Dave KG5CCI’s recent record breaking OSO with F4CQA through FO-29 on August 27th 2015, a distance of 7599.959 km and the satellite being just 0.2 degree above the horizon for both KG5CCI and F4CQA, some achievement !!

The evening finished off with a live demonstration of receiving AO-73 FUNcubes linear transponder using an FT-817 and a simple 2m dipole antenna.

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