All the "TV" satellites are Geosynchronus.<br />Meaning the satellite appears to stay in the same spot over the ground. (I hope you found the J-track link. It's a wonderful hands on example.)<br />Their orbit is 36000km above the equator. Called the Clark Belt (after Arther C Clark).<br />The orbit is much higher than the shuttle and other LEO low earth orbit satellites.<br /> From that orbit, a satellite can effectively cover 1/3rd of the earth's surface. Actually it is more like 1/2, but it's not real practical to have dish antenna's pointing at very low angles.<br /> In reality of course, satellites do not have "hemishperical beams" because there is no point to broadcast your signal into the ocean where nobody can pick it up. So their beams are more efficent and confined to area's of high population like the East coast of Australia. So even though you can see the Optus (Aussat) satellites from the ground in Japan and Australia. The beams are focused on Australia and you will never see the signal from them in Japan.<br /> At the same time, there is some 'spillover'.<br />For example in East Timor you can pick up Australian beam signals with a larger dish, even though you aren't considered in the footprint.<br /><br />There are currently 3 Optus satellites in service.<br />A3, B3 and C1. The A series satellites are the oldest. A1, A2 have used up all their fuel and were pushed into graveyard orbit. A3 is near the end of it's life. It's been put into an inclined orbit to help save fuel. The A series look like flying beer cans. There is some good pictures of the A2 being launched from the shuttle.<br />B2 was err.. lost after launch. I'm not sure how you lose 8 tonnes of satellite.<br />B3 is still in use and provides mostly paytv to NZ.<br />C1 was put into service April last year and the new D1 will be launched next year (and D2 in 2006).<br /><br />Fred's right .. you have lots more reading to do.<br />If you get yourself a cheap setup, hands on experience will help too.