Two kinds of satellite
FM satellites are a repeater in the sky. You transmit on one band (usually 2 m, at about 145 MHz) and hear the repeated signal on another (usually 70 cm, about 435 MHz). Only one station can use the channel at a time, so the contacts are brief: callsign and locator. They are the easiest way to start.
Linear transponders retransmit a whole slice of the band at once, so many SSB and CW stations can use it together. You listen to your own signal as you transmit and tune around. They need more skill and the satellite usually inverts the band, so tuning your transmit frequency up moves your signal down in the receiver.
Doppler shift
The satellite flies at about 7 km/s, so the received frequency rises as it approaches and falls as it leaves. On 70 cm the change is up to roughly ±10 kHz over a pass, and on 2 m about a third of that. For narrow-band FM you must tune as the pass goes on: start higher at AOS and move lower, and correct both your receive and your transmit frequency. The amateur satellites table shows the corrected frequencies for the moment the satellite is above your horizon.
Equipment and procedure
For FM: a dual-band handheld or mobile, a small directional antenna you can hold, such as a handheld three-element Yagi, and ideally a headset so you can aim and tune at the same time. Predict a pass on the pass predictor, choose one with a maximum elevation above 20°, be outside a few minutes before AOS, point the antenna towards the rising direction and follow the satellite across the sky. Call briefly with your callsign and wait for an answer.
Transmitting through an amateur satellite requires an amateur radio licence, and the rules differ from country to country. Listening generally does not, but check the local law.
Etiquette and checking status
Keep your transmissions short, listen before calling, do not use more power than needed and leave the channel to others after your contact. Satellite status changes: operators switch transponders off to save power in eclipse, and some satellites are silent for weeks. Check recent reports on the operators’ pages or at AMSAT before you plan, and use this site’s live radar to see which satellites are above you right now.
