Message-ID: <003b01bfce5c$0d1d4b80$05e11ac3@g4jnt>
From: "Andy Talbot" <drassew2@interalpha.co.uk>
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: GPS Frequency reference.
Date: Sun, 4 Jun 2000 20:35:28 +0100
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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.
>
>