Re: LF: GPS Frequency reference.

["Andy Talbot" <drassew2@interalpha.co.uk>]

One PPS output on the Garmin GPS25 is specified at 1us accuracy.  This ought
to be adequate if the PLL has a long enough time constant.  I use mine to
drive the B input of a counter timer and using teh A/B * 10^n functionm can
get gating times of 10000s

Have a look at the Brooks Sheera GPS Disiplined frequency standard in QST
last year or the year before sometime.  I've got a copy somwhere if you're
stuck

Andy  G4JNT


-----Original Message-----
From: Walter Blanchard <blanch@pncl.co.uk>
To: rsgb_lf_group@blacksheep.org <rsgb_lf_group@blacksheep.org>
Date: 04 June 2000 10:37
Subject: Re: LF: GPS Frequency reference.


> David,
>
> Your query:
>
> > I've been looking for a high stability source to act as a timebase for a
> > frequency counter and for a PLL reference.
> >
> > I notice that the older Magellan GPS300 is available at $ 99.
> >
> > Does anyone know if:
> >
> > 1)  The GPS300 has a 1Hz pulse output. (Or any other sensible frequency
with
> > high accuracy)
> >
> > 2)   It can display Maidenhead locators.
> I haven't been following this thread so not sure what you
> actually want these for, but a word of warning.
> These cheapo GPS's either (a) will not have any outputs,
> or (b) timing-wise they won't be worth a damn if you
> want any real accuracy.
> They use the cheapest VXO they can and depend on the
> software to hold time so it's very jittery.
> Are you looking for accurate relative time or accurate absolute
> time? - there's a big difference.
> Why don't you use MSF?  It's very easy to filter out
> the 60 kHz carrier and divide down to whatever you want -
> even I can do it!  And it's based on one of the frequency
> standards that USNO uses for GPS.
> You could always buy an MSF clock module from Maplin for
> a few quid and dig into it to pull out what you want.
> Have a word with Dr John Laverty at NPL - he supplies the
> controlling timing reference for MSF and is happy to talk
> to anyone about time and timing references.
>
> Walter G3JKV.
>
>
>
>
>
>
> Walter G3JKV.