[time-nuts] "Piezo Little Wonder" OCXO

[Jim Lux]

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" <James.P.Lux at jpl.nasa.gov>
>To: "Discussion of precise time and frequency measurement"
><time-nuts at 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.
> >
> >
> >
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