> >>Early GPS receivers used a 10.23 MHz time base.
>> >>Probably related to 2^10-1.
>> >
>> >
>> > yep.. the chip rate for the C/A code is 1.023 Megachips/second, the P
>> > code is 10.23 Megachips/second, and the L1 frequency (1575.42) is
>> > exactly 154 times the 10.23 MHz, the L2 is 120 times.
>> > So you can see that having a 10.23 MHz oscillator is a handy thing in
>> > a GPS receiver, especially if you can discipline it with the received
>> > signal.
>> >
>> > These days, one might choose a reference oscillator somewhat higher,
>> > so that when you do your 1bit A/D of the signal, you get many
>> > samples/chip, and so that the signal directly aliases to somewhere
>> > convenient. A lot of receivers use a sampling clock such that you get
>> > 1 bit I and Q samples at a convenient sample rate.  4*10.23 would
>> > work nicely, eh?  40.92 MHz
>> >