The Unexpected Revival of the AMSAT AO-7 Amateur Radio Satellite

AMSAT's AO-7, the second Phase 2 amateur radio satellite, was launched in November 1974 as a secondary payload on a Delta rocket alongside NOAA 4. After its battery pack failed in mid-1981, it was considered dead for roughly two decades — until a British radio amateur picked up an unexpected signal in 2002.

■ Satellite History
- AO-7's launch and nearly seven years of operation
- The nickel-cadmium battery short circuit that shut down the power system in 1981
- The satellite's status as inactive for around 20 years

■ The 2002 Signal Reception
- A British amateur scanning the 2-meter band for unauthorized transmissions finds slow Morse code at 145.97 MHz
- Doppler shift consistent with an orbiting source
- The classic AMSAT greeting and three-number telemetry groups in the old Oscar standard format

■ Telemetry and Diagnosis
- 24 channels covering battery voltage, current, and temperatures, designed for pencil-and-paper logging
- Confirmation via the AMSAT bulletin board and the frequency matching AO-7's old beacon
- Project manager John King's explanation for how the radio could run on solar power

Recommended for amateur radio operators, satellite enthusiasts, and anyone interested in spacecraft engineering or the history of the Oscar satellite program. It offers a concrete example of how a decades-old failure mode can be diagnosed from a received signal, along with background on the telemetry format used by early Oscar satellites. Viewing the full account is advised for the complete sequence of events and reasoning.