Amateur satellites are amateur stations in space. A station more than 50 km above the Earth is a space station, and your station on the ground, when it talks through one, is an Earth station (47 CFR 97.3). Any licensee may operate an Earth station within the privileges of their license class, and the authorized Earth station segments include 144 to 146 MHz and 435 to 438 MHz (47 CFR 97.209). AMSAT’s beginner guide shows that a dual-band handheld is enough to work an FM satellite (AMSAT FM guide).
Two kinds of satellites
FM satellites
An FM satellite works like a repeater in orbit: as on a repeater, only one station can transmit through it at a time (AMSAT operating practices). AMSAT recommends FM satellites as the place for beginners to start (AMSAT hints). Several satellites on AMSAT’s FM list need a CTCSS tone on the uplink, just like a terrestrial repeater (AMSAT live FM satellites).
Linear transponders
A linear transponder retransmits a whole slice of spectrum, so several SSB and CW contacts can share it at once, each on its own frequency (AMSAT). On AMSAT’s linear satellite list (updated March 24, 2026), the passbands of the satellites using 2 m or 70 cm range from 20 to 100 kHz wide. Most of those satellites are inverting, with an LSB uplink and a USB downlink (AMSAT live linear satellites). In an inverting transponder the signal’s position in the band is reversed, so a signal near the bottom of the uplink passband comes out near the top of the downlink (Extra pool question E2A02). Because the list gives SSB frequencies for both the uplink and the downlink, linear satellites need an SSB-capable station on both bands. A common guide for uplink power is that your signal on the downlink should be about as strong as the satellite’s beacon (Technician pool question T8B12).
Uplink, downlink and mode names
The uplink is the frequency you transmit on, and the downlink is the frequency you receive on (ARISS). Every satellite on AMSAT’s FM list (updated July 10, 2026) uses different bands for the two (AMSAT live FM satellites). Mode names give the uplink band first, then the downlink: V is 2 m and U is 70 cm, so a “U/V” satellite listens on 70 cm and transmits on 2 m (Technician pool question T8B08). AMSAT’s lists use the same letters, for example “V/u” for a 2 m uplink and 70 cm downlink (AMSAT live linear satellites).
Low Earth orbit and pass timing
A satellite in low Earth orbit (LEO) has an orbital period of around 100 minutes (Technician pool question T8B10). The ISS, for example, orbits about every 90 minutes, 16 times a day (NASA). AMSAT’s FM operating guide notes that a satellite is overhead for 15 minutes at most, and that distant stations are more likely to be in range at the beginning and end of a pass, when the satellite’s footprint is more likely to include them (AMSAT operating practices).
To know when to listen, use a pass predictor:
- AMSAT Online Satellite Pass Predictions lists passes for a satellite at your location, which you can enter as latitude and longitude or as a grid square.
- Heavens-Above and N2YO provide tracking and pass predictions.
Tracking programs calculate passes from each satellite’s Keplerian elements (Technician pool question T8B06). Keep them current; AMSAT notes that most programs are easily updated with tracking data from the internet (AMSAT FM guide). The grid square tool finds your locator.
Doppler shift
A satellite moves fast relative to you, and that motion changes the frequency you receive. This is Doppler shift (Technician pool question T8B07). Doppler shift is proportional to frequency, so it is larger on 70 cm than on 2 m (AMSAT).
For an FM satellite with a 70 cm downlink, AMSAT suggests starting about 10 kHz above the published downlink frequency, tuning down in 5 kHz steps as the signal gets scratchy, and ending about 10 kHz below it. The same guide shows those steps programmed as memory channels (AMSAT FM guide).
On linear satellites, the goal is for everyone in a contact to stay on one frequency at the satellite. Computer control can tune both radios to do this; when tuning by hand, the rule of thumb is to tune the radio on the higher frequency band, where the shift is larger (AMSAT).
A handheld station
AMSAT’s beginner guide describes a workable FM station (AMSAT FM guide):
- A dual-band 2 m and 70 cm handheld that can store split-frequency memories or has two VFOs.
- A better antenna than the stock “duckie”. A directional antenna, such as a handheld dual-band Yagi or log periodic, is an improvement over whips. Do not hold a whip straight up; tilt it to match the satellite’s elevation.
- Squelch wide open. FM satellites transmit at low power (about 250 mW for SO-50 in the guide’s example), so their signals are weak but readable.
- Headphones, and if possible a way to hear yourself on the downlink while you transmit.
With a directional antenna, about 5 W from a handheld is generally enough to work an FM satellite from horizon to horizon (AMSAT operating practices).
Example frequencies
On 2026-10-12, AMSAT’s FM satellite list (updated July 10, 2026) included these two:
| Satellite | Uplink (you transmit) | Downlink (you receive) |
|---|---|---|
| ISS FM repeater | 145.990 MHz, 67 Hz tone | 437.800 MHz |
| SO-50 | 145.850 MHz, 67 Hz tone | 436.795 MHz |
The same list notes that SO-50 has a 10 minute timer that you arm with a 2 second carrier carrying a 74.4 Hz tone before using it (AMSAT live FM satellites).
Checking what is working
The AMSAT Live OSCAR Satellite Status page collects reports from users around the world. For each recent day, each satellite and mode is marked active, telemetry or beacon only, not heard, or conflicting reports. Check it before a session, and add your own report after a pass so the next operator knows what to expect.
The ISS and ARISS
The International Space Station carries amateur radio equipment operated by the ARISS program. Crew members sometimes make unscheduled voice contacts during their personal time; the crew’s usual waking period is 0730 to 1930 UTC, and they are usually free most of the weekend. For crew voice contacts, ARISS lists a downlink of 145.80 MHz worldwide and an uplink of 144.49 MHz for ITU Regions 2 and 3, which include the Americas. Do not transmit on the downlink. Station call signs include NA1SS and RS0ISS (ARISS).
ARISS publishes which ISS radios are active. Its status as of October 7, 2026 showed the Columbus module radio (NA1SS) in voice repeater mode on the frequencies in the table above, and APRS active on 437.825 MHz from the radio in the Zvezda Service Module (RS0ISS) (ARISS status).
ARISS school contacts let students talk directly with an astronaut, in a contact that lasts about ten minutes (ARISS). Schools and other educational organizations apply through their ARISS regional representative, and selected groups are assigned a volunteer technical mentor. A contact can be direct, from an amateur station at the school, or a telebridge, where an ARISS ground station elsewhere makes the radio link and the audio is carried to the school by telephone. A school without a station may be able to work with a local radio club to set up a temporary station for a direct contact (About ARISS contacts).
Satellite etiquette
AMSAT’s two golden rules are: do not transmit if you cannot hear the satellite, and operate full duplex if you can, meaning you transmit and receive at the same time (AMSAT operating practices). The same guide adds:
- Share the pass. Make a contact or two, then listen.
- Let other contacts finish before you call.
- Do not call CQ on an FM satellite. Give your call sign and grid square, using phonetics.
- Give priority to stations operating portable from rare grid squares or countries.
- Use only the power you need. The rules require the minimum power necessary (47 CFR 97.313(a)), and excess uplink power on a shared satellite blocks other users (Technician pool question T8B02).
- Answer new stations; it may be their first satellite contact.
Identification rules apply to your Earth station, even though space stations are exempt from them (47 CFR 97.119). If FM simplex and repeaters are still new to you, start with making your first contact.