The 1200 bps Pacsats used an uncoded BPSK downlink on 70 cm and worked fine with 1/4-wavelength vertical antenna on the ground. As I remember, they only generated 1 watt of RF. A 2-meter downlink using an error correcting code would give 4 times the data rate with the same power. Digital voice now fits in 1200 bps so you could support APRS plus multiple voice channels.
73, John KD6OZH ----- Original Message ----- From: "Robert Bruninga" <[email protected]> To: <[email protected]> Sent: Sunday, September 27, 2009 14:42 UTC Subject: [amsat-bb] Re: All Satellites (Alan P. Biddle) >>> And wouldn?t it be a hoot if [these cubesats] >>> could put their RX/TX into a bent-pipe packet >>> mode, and then we would have amateur radio >>> global hand-held text messaging satellite system... >>> >>> Using some of the 2-way very small micro APRS >>> packet systems, a 2 to 5 Watt transponder will >>> easily fit... in a small cubesat. >>> See www.aprs.org/cubesat-comms.html >> >> If you could have maybe five or six cubesats >> with an FM transponder... [with] a good 15-minute pass >> every hour... would work wonders for getting people >> interested in satellites again. ... [with a] >> dual-band HT and a homebrew Arrow clone > > The beauty of the APRS packet text-messaging relay cubesat is > that it can have a 10 times higher power transmitter compared to > an FM voice transponder for the same average power budget. This > makes it workable on an HT with just a whip antenna, instead of > needing a handheld beam. Plus, each message takes one second > instead of 15 for each QSO. > > So that is why I prefer handheld packet text messaging as a > cubesat mission. Ten times the downlink power budget and 15 > times the number of contacts per pass. > > AO51 downlink could be 10 times as strong if the transmitter > would just drop when not in use... > > Bob, WB4APR > > > _______________________________________________ > Sent via [email protected]. 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 [email protected]. 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
