What is satellite communication in amateur radio?

Satellite communication in amateur radio involves using artificial satellites orbiting the Earth to relay and exchange radio signals between amateur radio operators. These satellites, commonly referred to as amateur radio satellites or OSCARs (Orbiting Satellite Carrying Amateur Radio), are designed and operated by amateur radio enthusiasts and organizations from around the world. They provide a unique and exciting way for amateur radio operators to communicate over long distances, even across continents, without relying on terrestrial infrastructure such as repeaters or ionospheric propagation.

Here are some key aspects of satellite communication in amateur radio:

Types of Amateur Radio Satellites

There are different types of amateur radio satellites, each with unique characteristics and capabilities:

• Low Earth Orbit (LEO) satellites: These satellites orbit at altitudes between 300 and 2,000 kilometers above Earth’s surface. They have short orbital periods, typically between 90 and 120 minutes, and are accessible for limited periods (usually 5 to 15 minutes) during their passes over a specific location. Examples of LEO satellites include the FM voice repeater satellites, such as the AO-91 and SO-50, and the linear transponder satellites, such as the XW-2 series.
• High Earth Orbit (HEO) satellites: These satellites orbit at much higher altitudes and have longer periods of visibility from a specific location on Earth. HEO satellites can provide continuous or near-continuous coverage over a large portion of the Earth’s surface, but they are more challenging and expensive to build and launch. The well-known AO-40 satellite was an example of an HEO satellite, but it is no longer operational.
• CubeSats and PocketQubes: These are small, lightweight satellites that have become popular in recent years due to their low cost and ease of deployment. Many educational institutions, research organizations, and amateur radio groups have built and launched CubeSats and PocketQubes for various purposes, including amateur radio communication.

Modes of Communication

Amateur radio satellites can support various communication modes, such as FM voice, single sideband (SSB) voice, Morse code (CW), and digital modes like packet radio or PSK31. Some satellites have crossband repeaters, which means they receive signals on one frequency band (e.g., VHF) and retransmit them on another frequency band (e.g., UHF).

Equipment and Antennas

To communicate via amateur radio satellites, you’ll need a suitable transceiver capable of operating on the satellite’s uplink and downlink frequencies, often in full-duplex mode (transmitting and receiving simultaneously). Many amateur radio operators use handheld transceivers or mobile rigs for satellite communication. In addition, you’ll need an appropriate antenna system, such as a handheld directional Yagi or a more advanced computer-controlled tracking antenna system, to track the satellite’s path across the sky and maintain a strong signal.

Tracking and Predicting Satellite Passes

To successfully communicate via amateur radio satellites, you need to know when a satellite will be within range of your location and its path across the sky. There are various software tools and smartphone apps available, such as Gpredict, Orbitron, or Heavens-Above, that allow you to track and predict satellite passes based on their orbital elements (known as Keplerian elements or Two-Line Elements, TLEs).

In conclusion, satellite communication in amateur radio offers a unique and exciting opportunity for radio enthusiasts to make contacts over long distances using space-based infrastructure. By understanding the different types of amateur radio satellites, their communication modes, and the equipment required, you can participate in this fascinating aspect of the amateur radio hobby and connect with fellow operators around the world.