AO-92 Update and Information on L-Band Downshifter

AO-92 Update and Information on L-Band Downshifter

It was day before yesterday that AO-92 which was thought to be inactive, was detected to be active again. A lot enthusiasm followed among the erstwhile operators on AO-92, with many relating their previous excellent experience with AO-92. Our local LEO Satellite Repeater Contact Group also sprung into action and all were ready to work the satellite. We were waiting for the pass at around 6.30 am UTC. But we had limitations as many of us had setup mainly for V/U satellites and not fully ready for a U/V transponder. Three or four of us could hear others on the AO-92 pass, but could not establish two way contacts. We decided to wait for the next suitable pass of the satellite. I could also find reports of contacts through the U/V transponder of AO-92 on Twitter and AMSAT Live Oscar Satellite status page. Many from our group also submitted status reports there. Incidentally, AO-92 is orbiting at an altitude lower than the international space station, with a perigee of 392.4 km and an apogee of 396.7 km, that is an almost circular orbit.

Meanwhile, I started collecting information on the L-Band downshifiter onboard AO-92, which intrigued me as I had not come across satellites with L/v transponders. My Twitter friend Andrew KE8FZT mentioned that: “They turned it on manually once a week for 24 hours for a while. It was hard to work portable because the Doppler adjustments were fast, but doable!” As per the AO-92 commissioning update on AMSAT webpage, the L-Band Downshifter would convert signals received on 1267.350 MHz and inject them into the satellite’s 435 MHz receiver. As the path loss expected for 1267 MHz was more and the satellite’s receive antenna was for 435 MHz, pre-launch estimate was that effective radiated power (ERP) of 100 Watts may be needed for horizon to horizon access in L/v mode. When the L-Band Downshifter was tested after launch, the author of that report could access it with 1 Watt power output to a 16 element commercial Yagi antenna for 23 cm. Audio clip of the AO-92 Mode L/v pass over North America is also available on the bottom of that page. It was really thrilling to hear the QSOs on L/v mode for the first time, though it was a recorded version, being accessed nearly 6 years later! Not sure whether they would turn on the L-Band downshifter again as the battery status is low and we have been asked to access the satellite only when illuminated.