RE: LF: Timing GPS

["Talbot Andrew" <ACTALBOT@mail.dstl.gov.uk>]

Well...

If you really want to play on the cheap and your ETrax has no PPS output, I suppose it is remotely feasible the leading edge of the NMEA string is probably consistent from second to second to within a few tens of microseconds - but you'd need to measure its absolute delay somehow which means having access to a true UTC related PPS

Perhaps we could do with a measurement session at some future LF Roundtable

There are (or at least were) some very cheap GPS modules on the surplus market - I got an Oncore from someone who had originally paid just a few pounds for it.

Andy  G4JNT

 

-----Original Message-----
From: G0MRF@aol.com [mailto:G0MRF@aol.com]
Sent: 2004 February 10 15:36
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: Timing GPS

In a message dated 2/10/04 12:35:33 PM GMT Standard Time, ACTALBOT@mail.dstl.gov.uk writes:

Well, I was really thinking of GPS locked PSK rather than any incoherent
mode.  WIthout the need for clock and frame timing recovery we could scrape
every possible advantage for coherent signalling.  With such superb accuarcy
of timing even without carrier recovery, it seems a pity to throw all the
advantages away by using on-off keyed power detection.

I did some basic tests last year with GPS locked 1 B/s PSK and with a very
simple decoder managed to receive down to frighteningly low signal levels.

Andy  G4JNT

Andy / group.

Would be happy to try this if there is a way of using the NEMA output from my e-trex venture. No problem with a little home constructing, but would prefer not to spend £86.

73

David

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