[time-nuts] GPS Crystal Frequencies
jimlux at earthlink.net
Tue Oct 27 19:22:03 EDT 2015
On 10/26/15 7:06 PM, Brooke Clarke wrote:
> I understand 10.230 MHz since when multiplied it gives 1176.45,1227.60,
> 1381.05 & 1575.42 MHz, all GPS carrier frequencies.
> But I've got a number of GPS receivers that have Rakon unit oscillators
> with a frequency of 10.949297.
> What's the story?
you might choose a frequency that when used as a direct sampler, causes
the GPS signal to alias to a convenient offset frequency (then all
Doppler shifts wind up being positive, for instance).
try 38.65 MHz for instance, that makes both L1 and L2 alias down to
around 9.2 MHz, which is slightly less than 1/4 of the sample rate, and
nicely accommodates the bandwidth of the signal
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