[time-nuts] GPSDO - probably a stupid question.

Nick Sayer nsayer at kfu.com
Wed Aug 17 12:28:35 EDT 2016

This would only likely be done for a GPS timing receiver, and even then likely only with something like a TCXO.

An ordinary GPS receiver can achieve positional results within modern spec without trimming its internal oscillator, and timing receivers solve the quantization problem by reporting the error rather than eliminating it.

Even if a GPS module had one, it wouldn’t get any better results with a more accurate oscillator, so the manufacturers don’t bother.

> On Aug 17, 2016, at 12:30 AM, Pete Stephenson <pete at heypete.com> wrote:
> On Aug 17, 2016 09:04, "Peter Reilley" <preilley_454 at comcast.net> wrote:
>> As a neophyte, I was wondering: rather that trying to discipline an
> external
>> oscillator to create a GPSDO and produce a precise 10 MHz why not
> discipline the oscillator
>> of the GPS receiver itself?   This could be done with a varactor diode
> across crystal of the
>> receiver's oscillator.   Of course there are the same problems with
> trying to servo this
>> oscillator as there are trying to servo an external oscillator but there
> are fewer parts.
> It's a very good idea, and is precisely what the Trimble Thunderbolt does
> with its 10MHz OCXO that it uses both as a system clock and a 10MHz output.
> Cheers!
> -Pete
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