Satellite AO-51 (known as Echo), NORAD number 28375 was created by ham radio operators and launched into a polar orbit on June 28, 2004. It takes about 100 minutes to orbit the earth at an altitude of 470 miles traveling at 17, 500 miles per hour. Since satellites travel at these tremendous speeds, ham radio operators must constantly change their receive frequency to match the Doppler effect. When a satellite is approaching your location, the receive frequency increases. As it goes away from you, the receive frequency decreases.  This is similar to the sound of siren on an ambulance as it passes you.

Ham radio operators use beam antennas to concentrate their transmitted signal to the satellite as well as concentrating the signal returning from the satellite.

The following conversation was recorded between me and Nick, KB1RVT in Burlington, VT. Nick and I were transmitting with HT’s at a power of about 5 watts! John, K8YSE in North Royalton, OH recorded the signals coming from the satellite at is home. The other station I spoke to was Brock, W6GMT, in Marcell, MN.

The letters and numbers you hear we use to identify our specific location are called grid square numbers which are part of the Maidenhead Locator System. Instead of exact latitude and longitude, the grid square will give you a very close point to your current position.