Notice: This page was initially generated with the assistance of AI and is pending human review. The information may contain errors or omissions. Amateur radio operators are encouraged to verify all technical details independently. Help improve this page by submitting corrections and additions. Learn how to contribute Remove this banner after human review is complete.
Amateur radio operators have been building and launching satellites since 1961, when OSCAR 1 (Orbiting Satellites Carrying Amateur Radio) became the first non-governmental satellite in orbit. Since then, well over 100 amateur satellites have been launched, and at any given time there are typically dozens in orbit providing a variety of communication capabilities.
AMSAT (the Radio Amateur Satellite Corporation) is the primary international organization that coordinates the design, construction, and launch of amateur radio satellites. Originally founded in the United States in 1969, AMSAT now has affiliated organizations in many countries, including AMSAT-UK, AMSAT-DL (Germany), AMSAT-NA (North America), and AMSAT-India. These groups collaborate to fund, build, and operate satellites for amateur radio use.
The OSCAR designation (Orbiting Satellites Carrying Amateur Radio) is assigned sequentially to amateur satellites. Each satellite receives a number upon reaching orbit — for example, AO-7 (AMSAT-OSCAR 7, launched in 1974) is one of the oldest still partially functioning.
FM satellites carry a simple repeater: they receive signals on one frequency (the uplink) and retransmit them on another (the downlink). Because they use FM — the same modulation that handheld radios use — they are the most accessible satellites for beginners.
The key limitation of FM satellites is that only one conversation can take place at a time, since FM captures the strongest signal. This means passes can be crowded, and operators need to keep transmissions short to share access. Good operating practice is essential.
Notable FM satellites have included SO-50 (SaudiSat-1C OSCAR 50), AO-91, AO-92, and various TEVEL and CAS series spacecraft. The specific satellites available change over time as new ones are launched and older ones fail.
Linear transponder satellites are more sophisticated. Instead of repeating a single signal, they retransmit an entire passband — typically 20–100 kHz wide. This allows multiple simultaneous contacts on different frequencies within the passband. Operators use SSB (single sideband) or CW (Morse code) on these satellites.
Working a linear transponder requires more skill than FM. You need to account for Doppler shift, manage your transmit power carefully to avoid capturing the transponder's AGC (automatic gain control), and tune continuously as the satellite moves.
Examples include FO-29 (Fuji-OSCAR 29), CAS-4A, CAS-4B, RS-44 (Radio Sport 44), and the QO-100 geostationary satellite.
Some amateur satellites carry digital payloads. These may include BBS (bulletin board system) mailboxes where messages can be uploaded on one pass and downloaded on a subsequent pass (store-and-forward), APRS digipeaters, or experimental digital transponders. The ISS also carries a packet radio digipeater that falls into this category.
The CubeSat revolution has dramatically increased the number of amateur satellites in orbit. Many universities and technical schools build small satellites (often 1U, roughly 10 cm × 10 cm × 10 cm) that carry amateur radio payloads as part of educational programmes. These satellites typically have shorter operational lifetimes than purpose-built AMSAT spacecraft, but they contribute to a dynamic and constantly changing satellite landscape.
Es'hail-2 (designated QO-100, or Qatar-OSCAR 100) is unique among amateur satellites because it sits in geostationary orbit at 25.5°E. Unlike other amateur satellites that orbit every 90–120 minutes and are only visible for a few minutes at a time, QO-100 is always in the same position relative to the ground. It is visible from a wide area covering Europe, Africa, the Middle East, India, and parts of South America and Southeast Asia.
QO-100 has two transponders: a narrowband transponder for SSB and CW on 10 GHz, and a wideband transponder for digital amateur television (DATV) on 10 GHz. Because the satellite does not move relative to your station, there is no Doppler shift and no need for tracking — you simply point a dish at the correct position in the sky.
Working through QO-100 requires 2.4 GHz uplink equipment and a 10 GHz downlink receiver, typically using modified satellite TV LNBs (low-noise block downconverters). The narrowband transponder can be received with a dish as small as 60 cm (24 inches) in many areas.
Most amateur satellites are in low Earth orbit (LEO), typically between 300 and 1,200 km (185–745 miles) altitude. At these altitudes, orbital periods are roughly 90–110 minutes, and a given satellite is visible from your location for only about 5–15 minutes per pass. The geometry of the pass — how high the satellite climbs above your horizon — determines the duration and signal quality.
Satellites in LEO are generally in one of several orbit types:
The easiest way to get started with amateur satellites is to work an FM satellite with a handheld radio:
Identify an active FM satellite. Check the AMSAT status page or satellite apps to find which FM satellites are currently operational. The available satellites change as new ones are launched and older ones cease functioning.
Predict a pass. Use tracking software to find when the satellite will be visible from your location. Look for passes with a maximum elevation of at least 20–30 degrees above the horizon for the best chance of success. Higher passes provide stronger signals and longer windows.
Program your radio. Enter the uplink and downlink frequencies for the satellite, including any required CTCSS (PL) tone on the uplink. Account for Doppler shift — the satellite's downlink frequency will be slightly higher than nominal as it approaches and slightly lower as it moves away. Many operators pre-program several frequency steps to manually correct for Doppler during the pass.
Track the satellite. When the pass begins, point your antenna toward the satellite's predicted position. Move the antenna to follow the satellite across the sky as the pass progresses. With practice, hand-tracking becomes second nature.
Listen first. Before transmitting, listen to learn the rhythm of the pass. You will hear other operators making contacts. Satellite operating style is fast and efficient because pass times are short — exchange callsigns, grid squares, and signal reports, then move on.
Make a contact. When you hear a gap, call CQ or respond to another station. Keep transmissions short. Use only enough power to be heard — excessive power on FM satellites can capture the repeater and block other users.
Because pass times are limited and many operators share the same satellite, good operating practice is critical:
The amateur satellite landscape changes frequently. Satellites are launched, activated, decommissioned, and sometimes revived. The best way to stay current is: