On 13 Oct 2013 at 18:30, Dave Marthouse wrote: > This isn't a question regarding amateur satellites but it is an interesting > theoretical one to pose here and the same laws of physics apply. I know > that the higher the frequency that is transmitted from a satellite the > larger the Doppler shift will be. The Iridium satellites transmit at around > 1.5gHZ. At that frequency I know the Doppler is large. How do they manage > to keep the portable handsets on the ground locked to the signal? Are the > handsets frequency agile to an extent? How do they achieve frequency lock > so that the digital signals are decoded? > > > > Dave Marthouse N2AAM > [email protected] > Interesting question Dave
I suspect as the XM/SIRIUS radio a data signal is sent back to the receiver position to minimized the doppler effect and some sort of data error correction also help to counteract the doppler effect. A similar system is implemented into the wxtoimg NOAA weather satellite fax decoding software. It is an educated guess who only need to be reeducated... Lets say my Sirius receiver in a plain flat field suffer some signal breaks that i can't explain. Luc Leblanc VE2DWE WAC BASIC CW PHONE SATELLITE _______________________________________________ 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
