Message-ID: <001101c3eff5$3a6920a0$6507a8c0@Main>
From: "Alan Melia" <Alan.Melia@btinternet.com>
To: rsgb_lf_group@blacksheep.org
References: <7D653C9C42F5D411A27C00508BF8803D01A9F415@mail.dstl.gov.uk>
Date: Tue, 10 Feb 2004 16:44:47 -0000
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Subject: Re: LF: Timing GPS
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Hi both look for the Radiosonde transmitters on eBay. I believe ther are two
types one with GPS and one without. They sell for about Ł12. The GPS module
does not supply all the nmea strings but it does have time and 1 sec ticks I
believe.

Cheers de Alan G3NYK
alan.melia@btinternet.com

----- Original Message -----
From: "Talbot Andrew" <ACTALBOT@mail.dstl.gov.uk>
To: <rsgb_lf_group@blacksheep.org>
Sent: 10 February 2004 15:56
Subject: RE: LF: Timing GPS


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 Ł86.

73

David


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