From: Hal Murray <[EMAIL PROTECTED]> Subject: Re: [time-nuts] Carrier phase tracking Date: Mon, 19 Feb 2007 12:34:33 -0800 Message-ID: <[EMAIL PROTECTED]>
> > > But... as marketing people thinks that 'more satellites, better' some > > manufactures are commercializing small GPS receivers with 16 and even > > 20 channels... and obviously, no advantage over 12-channel ones. > > Perhaps they expect the Navstar constellation to be so crowded in the > > near future to don't let the Sun rays reach the Earth :-) > > How many satellites are there in the Russian or European systems? GPS: 31 sats GLONASS: 13 sats GALILEO: 0 sats (but they have a test-sat) Those numbers are from the CODE tracking, but they track sats being taken out of active constellation, so more real numbers comes from more official sources: GPS: 30 active sats (SVN15/PRN15 is taken out) GLONASS: 14 active sats GALILEO: 0 active sats. > Or will there be if/when everything gets fully deployed? GPS: 32 (?) sats (sats lasting longer, published codes running out, etc.) GLONASS: 24 sats @ 2010 GALILEO: 27 sats > How close are the frequencies? Traditional GPS and traditional GLONASS have separated footprints, but close enought for common solutions. Modern GPS and GALILEO share foot-print but GALILEO has additional frequencies. Modern GLONASS adds another frequency. > What's the bandwidth of the signal? It is a matter of traditional to modernized and upcomming. 2,046 MHz for traditional GPS C/A code, but it actually extends to 20,46 MHz and you can get additional benefits for accepting a larger window at the cost of reduced jamming suppression. The benefit being better multipath performance. > How far does doppler shift things? GPS-L1 you can see shifts like 6-7 kHz on the L1 carrier. > Is there spectrum set aside for this use, or is it shared with other > applications and the receiver has to dig the signal out of a mess that's > worse than just noise? The spectrum is set aside, but there have been attempts to make use of it from several directions, UWB is only one. There is a hole in the middle set aside from radioastronomers, who don't like the L3 transmissions. Cheers, Magnus _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts