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 <[email protected]>
To: [email protected] <[email protected]>
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.