Historical 10m Activity on Satellites!

Currently amateur radio satellite activity is on VHF, UHF and SHF. Former two being for Low Earth Orbit (LEO) satellites and SHF for Qatar Oscar 100 Geostationary Amateur Radio Satellite. But there was an era when there was satellite activity on 10m or 28 MHz, though I don't think any such transponder is currently active. AMSAT-OSCAR 7 which was launched on November 15, 1974 and still continues to be partially active, is one of the satellites which was active on 10m band. It had a Mode A transponder with 145.850-950 MHz uplink and 29.400-500 MHz downlink. and Mode B transponder with 432.180-120 MHz uplink and 145.920-980 MHz downlink. These are linear (SSB/CW) inverting transponders. In addition it had 29.500 and 145.700 MHz beacons. There was also a 2304.1 MHz beacon which was never turned on because of international treaty constraints. 


In 1981, AO-7 had become non-operational due to battery failure. But surprisingly, in 2002, one of the shorted batteries became an open circuit and the space craft was able to run on solar panels. So it would not be usable in eclipse. When continuously illuminated, it can alternate between A and B modes every 24 hours. A look at AMSAT Live OSCAR Satellite Status Page tells me that only Mode B is operational currently, that is a U/V linear transponder with uplink on UHF and downlink on VHF. It is interesting to note that the 432 MHz uplink for AO-7 was designed before implementation of the 435-438 MHz satellite sub band. Operation in the United States is currently 'grandfathered' under a waiver from the FCC.

Another instance of 10m activity by a satellite or rather a spacecraft was from Juno, which was on its way to Jupiter. Global amateur radio community had participated in a challenge during its Earth fly by over a decade back. Earth fly by was to give Juno a gravity assist to to send it to Jupiter. VU2JOS had posted a QSL card confirming his participation in the event. The event was on 9th October 2013, when over 1400 amateur radio operators around the world transmitted "HI" in Morse Code, repeatedly, in unison. Simultaneous global transmissions were needed to ensure that the signal reaches the spacecraft. It was also a way to engage the global community in the space program. Radio amateurs used two webpages provided by NASA to synchronize their transmissions. NASA could extract the Morse Code signals transmitted on 28 MHz and decode it after sieving out the background noise. The image from NASA website shows decoded signals. 

This is the accompanying video clip from NASA website. The event was termed HI JUNO experiment and it was a coordinated effort of NASA and the global amateur radio community.


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