When OSCAR-7 (Orbiting Satellite Carrying Amateur Radio) was launched on 15 November 1974, few could have predicted its longevity. Nearly 50 years later, this amateur radio satellite holds the distinction of being the oldest operational satellite still functioning in orbit. This remarkable achievement underscores the ingenuity and resilience of the amateur radio community and serves as a testament to the enduring relevance of OSCAR-7 in space and communication history.
A Historic Achievement
Developed by AMSAT (Radio Amateur Satellite Corporation), OSCAR-7 was launched to replace its predecessor, OSCAR-6, and to advance global amateur radio communications. Its launch aboard a Delta 2310 rocket from Vandenberg Air Force Base in California marked a significant milestone for amateur radio enthusiasts worldwide.
While many satellites launched during its era have long since ceased operation, OSCAR-7 continues to surprise and inspire. Its unexpected revival in 2002—after a 21-year hiatus—secured its place as a symbol of durability and innovation in satellite design.
Why OSCAR-7 Matters Today
OSCAR-7’s legacy lies in its continued ability to facilitate amateur radio communication despite its age. Its robust design and the resilience of its systems allow it to serve as a valuable resource for amateur radio operators, providing a platform for long-distance communication and experimentation.
Resilient Design: OSCAR-7 was designed with redundancy and durability in mind. After its onboard batteries failed in 1981, it was presumed lost. However, the satellite’s solar panels continued to function, and in 2002, a fortuitous power reset restored it to operational status.
Operational Role: Today, OSCAR-7 remains active in providing transponder capabilities for amateur radio operators worldwide. It supports both voice and Morse code communication, maintaining its relevance in the amateur radio community.
Coverage and Usage
One of the most remarkable aspects of OSCAR-7 is its coverage area. As it orbits at an altitude of approximately 1,450 kilometres in a polar orbit, the satellite provides global coverage during its passes. Operators within the satellite’s footprint—often spanning thousands of kilometres—can communicate with one another, making OSCAR-7 a valuable resource for establishing long-distance connections.
Coverage Footprint: OSCAR-7’s signals can cover large portions of the Earth, depending on its position. For a few minutes during each pass, it can connect operators separated by thousands of kilometres, enabling global communication for amateur radio enthusiasts.
Day-to-Day Usage: Despite its age, OSCAR-7 remains well-used by the amateur radio community. Enthusiasts often take advantage of its transponders for testing equipment, experimenting with satellite communication, and making contacts across borders. Its linear transponders allow multiple simultaneous signals, making it a favourite for operators interested in voice, CW, or digital modes. While it doesn’t have the traffic of modern satellites, its historical significance and unique operational status ensure it remains active daily.
How to Use OSCAR-7
One of the most exciting aspects of OSCAR-7 is that it remains accessible to amateur radio enthusiasts with relatively modest equipment. Here’s how you can utilise this historic satellite:
Understanding Its Capabilities: OSCAR-7 features two primary transponders that amateur radio operators can use:
- Mode A: Uplink on 2 metres (145.850–145.950 MHz) and downlink on 10 metres (29.400–29.500 MHz).
- Mode B: Uplink on 70 cm (432.125–432.175 MHz) and downlink on 2 metres (145.925–145.975 MHz).
Equipment You Need: To communicate with OSCAR-7, you’ll need:
- A VHF/UHF transceiver capable of operating on the uplink and downlink frequencies.
- A directional antenna, such as a Yagi, to track the satellite as it moves across the sky.
- Satellite tracking software or an app to predict OSCAR-7’s pass times and calculate its position.
Making a Contact:
- Track the Satellite: Use satellite tracking software to identify when OSCAR-7 will be overhead. Aim your antenna at the satellite’s location.
- Set Frequencies: Tune your transceiver to the appropriate uplink and downlink frequencies for the chosen mode. Remember to adjust for Doppler shift as the satellite moves.
- Transmit and Listen: Call CQ using your callsign and listen for responses on the downlink frequency. OSCAR-7’s transponders are linear, so you can also experiment with SSB or CW modes.
What Makes OSCAR-7 Unique?
OSCAR-7 operates passively, meaning it relies solely on its solar panels for power. This means it only functions when it is in sunlight. As an open-access satellite, it provides an excellent opportunity for newcomers to learn about satellite communication and for experienced operators to test their skills. Its robust design and operational simplicity make it a fantastic learning tool and a historic marvel.
Technical Highlights
OSCAR-7 was a marvel of its time, featuring:
- Multiple Transponders: Two Mode-A transponders and one Mode-B transponder, allowing global amateur communication.
- Beacons: Beacons transmitting telemetry data for tracking and research purposes.
- Innovative Power Systems: Solar panels capable of sustaining operation even after battery failure.
A Testament to Amateur Radio Ingenuity
The story of OSCAR-7 is not just one of technological achievement but also of the collaborative spirit that defines amateur radio. Its development was funded and supported by enthusiasts from around the globe, highlighting the passion and resourcefulness of the amateur radio community. Its unexpected revival in 2002 further reinforced the value of curiosity and perseverance in science and engineering.
Join the Legacy
OSCAR-7’s continued operation is an incredible opportunity for amateur radio operators to connect with a piece of history. Whether you’re making your first satellite contact or revisiting its legacy, OSCAR-7 offers a unique experience that combines the thrill of communication with the nostalgia of space exploration.
Get your equipment ready, track the next pass of OSCAR-7, and become part of its enduring story. This satellite isn’t just a piece of history—it’s a living part of the amateur radio experience.
73,
The HADARS Committee