At 10:37 AM 5/30/2008, you wrote: >I have two PIEZO 10.230 MHz crystal oscillators in the same style package as >the 10811. But the oscillator in question is for 10.238 MHz.
interesting.. is the 8kHz a deliberate offset? Is the manual tuning off to one end? Maybe they were using them in a scheme where instead of I/Q they did offset IF sampling. >John WA4WDL > >----- Original Message ----- >From: "Jim Lux" <[EMAIL PROTECTED]> >To: "Discussion of precise time and frequency measurement" ><time-nuts@febo.com> >Sent: Friday, May 30, 2008 12:47 PM >Subject: Re: [time-nuts] "Piezo Little Wonder" OCXO > > > > At 08:33 AM 5/30/2008, you wrote: > >>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 > > > > > > > >>Some GPS manufacturers approached HP about making > >>a 10811 on 10.23 MHz. There is a circuit modification > >>for 10.23 MHz and some crystals were made (I > >>have some somewhere). However, I don't believe > >>any 10.23 MHz 10811's were sold. This unit was > >>probably intended to meet the need not filled by HP. > > > > > > > > _______________________________________________ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > > > >_______________________________________________ >time-nuts mailing list -- time-nuts@febo.com >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.