At 02:50 AM 4/12/2011, Phil Karn wrote: >To elaborate: >... >As I recall, ARISSat-1 data frames can be up to 512 bytes long. Ignoring >HDLC flags, bit stuffing, CRC, etc, that's 4K bits. At a data rate of 500 >bps (the FEC is rate 1/2), 512 bytes will take 4096/500 = 8.192 seconds to >transmit. > >8.192 seconds is longer than 7.232 seconds. > >Ooops. > >But wait, there's more. If the satellite sends a series of back-to-back 512 >byte frames, and the transmitter comes on too late after one has already >started, you'll have to wait for it to end before you can begin decoding the >next one. Meanwhile, the clock is quickly ticking down until the transmitter >goes OFF again... > >Double oops.
Hi Phil, That's why it doesn't work that way. In low power mode, the transmission is started clean every time. A single telemetry data frame is only 256 bytes so about 4 seconds of data. After the 1 frame, the transmitter is left on until the interleaver is emptied. 73, Tony AA2TX _______________________________________________ Sent via AMSAT-BB@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
