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AO-7 Still Going Strong after Almost 42 Years in Space

10/04/2016

In a little more than a month, the venerable AO-7 Amateur Radio satellite will mark 42 years in space. AMSAT says AO-7, the oldest ham radio satellite still in operation, is now switching between Mode A and Mode B on a daily basis, after coming up in Mode A on September 30.

“That suggests that the satellite is now in constant sunlight and receiving enough power from the solar cells for the 24-hour timer to stay on throughout its entire orbit,” AMSAT-NA Secretary Paul Stoetzer, N8HM, said. “Expect daily mode switches between Mode A and Mode B to occur for the next three months or so. As AO-7’s orbit precesses and the periods of constant sunlight become fewer and fewer, there will be less of an opportunity to use Mode A on a yearly basis, so enjoy it while it lasts!”

In Mode A, earthbound amateurs transmit on 2 meters and receive on 10 meters. Stoetzer said the type of 10 meter antenna isn’t fussy. “Try whatever you can,” he said. When continuously illuminated, AO-7’s mode will alternate between Modes A and B (70 centimeters up/2 meters down) every 24 hours.

November 15, will mark 42 years since AO-7 was launched into space from Vandenberg Air Force Base in California. AO-7 was the second so-called “Phase 2” Amateur Radio satellite that AMSAT-NA constructed and launched into low-Earth orbit. It remained in operation until a short circuit occurred in a battery in 1981. More than 20 years later, however, AO-7 unexpectedly returned to life, its 2 meter beacon showing up on 145.9775 MHz.

AMSAT describes the Mode A/B spacecraft as “semi-operational” and dependent upon its solar panels for a reliable power source; AO-7 works only as long as its solar panels are illuminated by sunlight. Satellite experts speculate that AO-7’s resurrection occurred when the short circuit in the battery opened up for some reason, allowing the solar cells to power the spacecraft. When the satellite goes into eclipse, it powers down.

Since the satellite came back to life, terrestrial users have enjoyed numerous contacts via AO-7. Last February Dave Swanson, KG5CCI, of Arkansas achieved a distance milestone on AO-7 using Mode B to work Eduardo Erlemann, PY2RN (GG66lw), in Brazil — 8030.895 kilometers — which Swanson said was “way beyond the theoretical range AO-7” and a feat that “the math said shouldn’t be possible.”

AO-7 has beacons on 29.502 MHz (used in conjunction with Mode A) and, nominally, on 145.972 MHz (used in conjunction with Mode B and Mode C — low power Mode B). The 435.100 MHz beacon has an intermittent problem, switching between 400 mW and 10 mW. — Thanks to AMSAT-NA, AMSAT News Service 



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