ISS crossband repeater operations

The ISS has been operating with an uplink of 1269.650 MHz and downlink of 145.800 MHz. There have been many QSO's via this repeater mode along with interesting reports about doppler effects, signal strength etc.

Many have been posting reception reports and comments
after successful contacts on the AMSAT-BB e-mail list for those of us to enjoy that may not have the equipment to operate with.

Mike, N1JEZ reported, "I got on the ISS Repeater this morning during the 1127 UTC pass here in Vermont FN34im. I took the opportunity to play with doppler/power/antenna alignment/modulation etc. As suspected, everything needs to be pretty much right on for good access. By paying close attention to AZ/El and Doppler, I was able to hold the repeater down to less than 5 degree El.

Even at my power level, being 2-3 kHz off seemed to be the maximum error on doppler. Power here was set at approximately 5 kW EIRP. I did drop 10 dB and still got in as the ISS passed overhead. My full power setup here includes 80 watts in the shack to a 55 element 1269 MHz Directive Systems loop yagi. My transmission line is 75' of 7/8" hardline."

Alan, WA4SCA said, "I have about 2500 watts EIRP on L-Band, minus some attenuation from trees, and could only bring it up above 45 degrees. The limiting factor seemed to be having enough radiated power to break the squelch. I determined that the uplink frequency needs to be properly
centered. On AO-51 I can go ± 5 kHz and still get it, whereas with the ISS I got nothing, even around TCA. ± 3 kHz is probably more like it, and of course depends on your power."

Clare, VE3NPC wrote, "NA1SS heard my reply to his CQ and congratulated me on being the first station heard via L-band but unfortunately he didn't get my call right and I wasn't able to get in again on that pass." He was able to work N1JEZ and other stations on later passes.

Frank, IW4DVZ running and FT-736R + PA output of 40 watts on L-Band FM into antenna consisting 2x35 elements linear polarization and manual doppler compensation worked Fer, IW1DTU. Fer was running a TS-790 with 60 watts output into 55 element yagi on L-Band.

David, G8OQW running an Icom 910 into a horizontal 19 element yagi on a tripod mount on his patio reported, "At 60 degrees elevation I just made it in but very briefly and with a very scratchy signal. On January 1, I had and excellent pass, accessed repeater at best range yet, 750Km still using only 170w max ERP from tripod mounted 19 element
horizontal yagi."

Jeff, K7WIN reported working Ron, N6PAA on January 1,
"I could hear you for over 2 minutes prior to our QSO and our QSO lasted just about 2 minutes. I couldn't get in until ISS was above 15 degrees as I only have 10 watts on L Band."

Frank, KA3HDO
AMSAT-NA V.P. for Human Spaceflight Programs
and ARISS International Chairman

Source: Amsat

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