[time-nuts] 5370B on eBay, carrier phase tracking GPS receiver

Magnus Danielson cfmd at bredband.net
Sun Feb 18 23:12:59 EST 2007

From: Dr Bruce Griffiths <bruce.griffiths at xtra.co.nz>
Subject: Re: [time-nuts] 5370B on eBay, carrier phase tracking GPS receiver
Date: Mon, 19 Feb 2007 16:53:55 +1300
Message-ID: <45D91F53.8080405 at xtra.co.nz>

> Brooke Clarke wrote:
> > Hi Bruce:
> >
> > Is there a paper describing the method?
> >
> > Have Fun,
> >
> > Brooke Clarke
> >
> > Have Fun,
> >
> > Brooke
> >
> > w/Java http://www.PRC68.com
> > w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml
> > http://www.precisionclock.com
> >
> >
> >
> > Dr Bruce Griffiths wrote:
> >
> >   
> Brooke
> Yes I think that Magnus posted it some time ago:
> http://tycho.usno.navy.mil/ptti/ptti99/PTTI_1999_405.PDF

There is another paper just before it. There is also a patent for a specific
form of implementation.

> Note they used an Oncore VP, the Superstar has a better carrier phase 
> tracking.performance.

What they did was that they hooked their Oncore VPs up to cesium beams for
test purposes. Locking that clock with a not-so-perfect but sufficient for
the task ratio.

You can do about the same without too much difficulty, but the Allstar,
Superstar and Superstar II receivers belong to those that is built out of the
Zarlink chipsets which all feature an interesting issue, the use of a 10 MHz
TCXO. Now, this frequency should be fairly know to us time-nuts, no? ;)

Wiring in an externally supplied 10 MHz should not be all that difficult.
The receiver is now effectively a high resolution phase comparator between the
selected sats and the timing source used for reference. The PPS output of the
receiver is not used for reference, but rather the carrier phase pseudo-ranges.
Either you tap the pseudo-range data out and do the dirty stuff outside, or
you have the receiver do all the calculations. Having a reciever do some
interesting corrections on pseudoranges may be a bit harder thought.

Anyway, if you do things properly, it will be a much better solution than
looking at that PPS.


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