The Healthy Growth of
Amateur Radio Satellites in the 1970s


Amateur Radio operators around the world continued to build and send hamsats to orbit in the 1970s. Here is a summary in chronological order of the next six Amateur Radio satellites, launched in the 1970s:

1970: OSCAR-5

OSCAR-5, also known as Australis-OSCAR-5, was designed and built by students in the Astronautical Society and Radio Club at the University of Melbourne, Australia.

AMSAT managed launch of the satellite January 23, 1970, from Vandenberg Air Force Base, California, to a 925-mile-high polar orbit aboard a Delta rocket ferrying an American weather satellite to space.

OSCAR-5 had telemetry beacons transmitting seven kinds of data about the satellite at 29 and 144 MHz. It was the first amateur satellite to be controlled from the ground. It contained a command receiver which allowed ground stations to turn on and off its 29 MHz beacon transmitter.

OSCAR-5 had no solar cells and no two-way transponder, but it did have a magnetic attitude-stabilizing system. Telemetry operated only 52 days, however OSCAR-5 remains in space.

1972: OSCAR-6

OSCAR-5 was the last of the first generation of hamsats. OSCAR-6 started a second generation of Amateur Radio satellites known as Phase-2.

Parts of OSCAR-6 had been built in the U.S., West Germany and Australia and critical parts had redundant back-ups. It was launched to a 900-mile-high orbit alongside a government weather satellite on October 15, 1972.

The satellite's two-way communications transponder received signals from the ground on 146 MHz and repeated them at 29 MHz with a transmitter power of one watt. Low-power ground stations with simple antennas were successful in using the satellite.

OSCAR-6 had a sophisticated telemetry beacon which reported information about many parts of the spacecraft, including voltages, currents and temperatures. Where OSCAR-5 had seven kinds of data reported in its telemetry beacon, OSCAR-6 had 24. OSCAR-6 had a magnetic attitude-stabilizing system.

OSCAR-6 also had an elaborate ground-control system to turn off parts of the satellite selectively. The hamsat could react to 35 different commands from ground stations in Australia, Canada, Great Britain, Hungary, Morocco, New Zealand, West Germany and the United States.

Codestore was a digital store-and-forward message system built into the hamsat. Ground controllers in Canada sent messages to the satellite which were stored and repeated later to ground control stations in Australia.

Static in the satellite affected its computer which read the noise as a command to shut down. To overcome the problem, controllers sent a continuous stream of ON commands to the satellite to keep it turned on. Where OSCAR-5 had been commanded twice a week, OSCAR-6 received 80,000 a day. The trick worked. The solar-charged batteries allowed the radio to work 4.5 years in orbit. OSCAR-6 remains in space today.

1974: OSCAR-7

Artist concept of OSCAR-7
Artist concept of OSCAR-7
Artist concepts of AMSAT-OSCAR 7 in space
Source: Phil Karn KA9Q – photos and art collected by Dick Daniels, W4PUJ, during construction, testing and launch in 1973 and 1974. Click image to enlarge


Amateur Radio had two working satellites in orbit for the first time after OSCAR-7 was launched November 15, 1974. It was a second Phase-2 satellite, similar to OSCAR-6, but with improvements. For instance, OSCAR-7 had two transponders. One received at 146 MHz and repeated what it heard at 29 MHz while the other listened on 432 MHz and relayed the signals on 146 MHz. The latter had an eight-watt transmitter and was built by radio amateurs in West Germany.

In the first satellite-to-satellite link-up in history, a ham transmitted to OSCAR-7 which relayed the signal to OSCAR-6 which repeated it to a different station on the ground.

Australians built a telemetry encoder for the satellite and Canadians built a 435 MHz beacon.

Other beacons were at 146 MHz and 2304 MHz. The 2304 MHz beacon, with a transmitter power of 100 milliwatts, was built by the San Bernardino Microwave Society of California. Unfortunately, the FCC denied the hams permission to turn on their 2304 MHz beacon so it never was tested in space.

OSCAR-7's radio system worked 6.5 years. Then it stopped functioning.

However, after more than two decades of silence, OSCAR-7's radio came back to life in 2002.

Both operating modes A and B function, but the satellite's control system is not working. Even though it can't be controlled from the ground, OSCAR-7 supports conversations on most passes overhead every day.

The satellite remains in space and it continues to be one of the most enjoyable satellites to use today.

1978: OSCAR-8

The third Phase-2 hamsat was launched March 5, 1978, on a Delta rocket from Vandenberg Air Force Base, California, to a circular 570-mile-high polar orbit. OSCAR-8 spun around the globe every 103 minutes.

It had two transponders, including one designed by Japanese radio amateurs. It listened at 146 MHz and repeated what it heard through a transmitter on 435 MHz. The rest of the hardware was built by American, Canadian and West German amateurs.

Phase-2 fun continued for 5.3 years while OSCAR-8's radio worked. Unfortunately, its batteries died in the middle of 1983. OSCAR-8 remains in orbit today.

1978: Radiosputniks 1 and 2

The USSR's Sputnik had launched the Space Age in 1957, but Russian hams had been only spectators as Western radio amateurs launched seven OSCARs between 1961 and 1978.

In the mid-1970s, Soviet amateurs found themselves among engineers visiting the United States in preparation for the 1975 Apollo-Soyuz joint flight. While visiting NASA's Goddard Space Flight Center, Russian hams discussed OSCARs with AMSAT members.

Word of a USSR amateur satellite program leaked from behind the Iron Curtain in a 1975 article in the Russian electronics magazine, Radio. Transponders were said to be under construction in Moscow and Kiev.

In 1977, the USSR government notified the International Frequency Registration Board that a series of hamsats would be launched. Radio magazine Radiosputnik (RS) hamsats.

A Russian F-2 rocket blasted off October 26, 1978, from the Northern Cosmodrome at Plesetsk carrying a government satellite and the first two Soviet hamsats-RS-1 and RS-2-to elliptical orbits 1,000 miles above Earth.

Each had a 145-to-29 MHz transponder. The satellites, sometimes also referred to as Radio-1 and Radio-2, circled the globe every 120 minutes.

The satellites transmitted a telemetry beacon in Morse Code, reading out temperature and voltage data. The hamsats had solar cells as well as a Codestore message store-and-forward mailbox. Ground control stations were at Moscow, Novosibirsk and Arseneyev near Vladivostok.

The satellites had very sensitive receivers and overload fuses to flip off whenever a ham on the ground would use excessive transmitter power. The circuit breaker could be reset from the ground when over the USSR. Western hams, transmitting thousands of watts of power, kept tripping the fuses and turning the Radiosputniks off. The Russian ground controllers kept resetting the circuit breakers, but most operation ended up being over the Soviet Union since Western hams kept shutting off the transponders when the satellites were over North America and Western Europe.

The Radiosputniks each weighed 88 lbs. and were cylinders 17 in. in diameter and 15 in. long. The batteries in RS-1 lasted only a few months. However, RS-2 was heard until 1981. Today, they are dead in orbit at altitudes around 1,050 miles.

Even in today's openness, we don't know for sure there was not a failed Radiosputnik prior to RS-1. We do know many more Radiosputniks were to come as well as three USSR hamsats known as Iskra or "spark" in Russian.

Table listing all amateur radio satellite launches »»

Hamsat Chronology.

The next page continues this amazing story of Amateur Radio satellites with the seventeen hamsats, launched in the 1980s:

The 1960s
The 1980s

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