Why is pcsat having so much trouble carrying its 5 watts then? Even when the satellite is in full sun? Even on the Z panel? I'm not complaining, I just want to understand what went wrong.
73 de KA9SCF. On Sep 3, 2009, at 17:34, "Robert Bruninga" <bruni...@usna.edu> wrote: >> To get good coverage you need as many >> LEO satellites as possible so they should >> each be as small as possible. >> Intersatellite linking could be done >> via automated ground stations. This >> eliminates the need for high-power >> transmtters and/or high-gain antennas >> on the satellites for interlinkng. > > Yep, that is what we have been trying to do now for 8 years with > the APRS satellites on 145.825. We just need several of them in > orbit at the same time. We have demonstrated dual-hops several > times whenever two or more of the APRS satellites (and ARISS) > are operational at the same time. If we could get 6 to 10 of > the University cubesats to simply carry the 3.4" square APRS > transponder (Byonics TinyTrck-4), then we would have a > constellation providing nearly continuous connectivity via these > satellites from any handheld or mobile APRS radio. With 6, you > might have to wait 30 minutes or so to make yoru contacts. With > 10 or so, you might have to wit no more than 5 to 10 minutes for > connectivity. > > See www.aprs.org/cubesat-comms.html > >> It's better to put that gain and power >> consumption on earth. > > The advantage of the APRS satellite concept and Packet, is that > we can use a 5 Watt transmitter on the satellite to be able to > hit any mobile or HT using its existing omni antenna because the > packet has a low dutycycle. So running 5 watts on a cubesat is > easy, because the transmitter dutycycle is only on less than say > 5% of the whole-orbit time. (average power 1/4 Watt) > > Whereas ECHO which is on all the time, has to be set at 1/4 watt > TX power because it is on all the time. > > Also, EVERY APRS satellite would be on the same frequency > 145.825 with no doppler to track, and since every one of them > does the same generic relay, independent of callsign, then the > user on the ground just operates... He does not have to do > anything to go from one satellite to another... > > Bob, WB4APR > > _______________________________________________ > Sent via amsat...@amsat.org. Opinions expressed are those of the > author. > Not an AMSAT-NA member? Join now to support the amateur satellite > program! > Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb _______________________________________________ Sent via amsat...@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
