[time-nuts] "Piezo Little Wonder" OCXO
jmfranke at cox.net
Fri May 30 13:37:51 EDT 2008
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.
----- 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
> 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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