Return-Path: Received: (qmail 58000 invoked from network); 10 Feb 2004 15:56:38 -0000 Received: from unknown (HELO ptb-mxscan03.plus.net) (212.159.14.237) by ptb-mailstore01.plus.net with SMTP; 10 Feb 2004 15:56:38 -0000 Received: (qmail 91224 invoked from network); 10 Feb 2004 15:57:46 -0000 X-Filtered-by: Plusnet (hmail v1.01) X-Priority: 3 X-MSMail-Priority: Normal X-Spam-detection-level: 11 Received: from ptb-mxcore03.plus.net (212.159.14.217) by ptb-mxscan03.plus.net with SMTP; 10 Feb 2004 15:57:45 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore03.plus.net with esmtp (Exim) id 1AqaGe-000NIV-E1 for dave@picks.force9.co.uk; Tue, 10 Feb 2004 15:57:44 +0000 X-Fake-Domain: majordom Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1AqaFs-00016o-NS for rs_out@blacksheep.org; Tue, 10 Feb 2004 15:56:56 +0000 Received: from [192.5.29.49] (helo=relay.dstl.gov.uk) by post.thorcom.com with smtp (Exim 4.14) id 1AqaFs-00016f-1w for rsgb_lf_group@blacksheep.org; Tue, 10 Feb 2004 15:56:56 +0000 Received: (qmail 26039 invoked from network); 10 Feb 2004 15:56:55 +0000 X-Fake-Domain: unknown Received: from unknown (HELO warlock.dstl.gov.uk) (192.5.29.10) by relay.dera.gov.uk with SMTP; 10 Feb 2004 15:56:55 +0000 Message-ID: <7D653C9C42F5D411A27C00508BF8803D01A9F415@mail.dstl.gov.uk> From: "Talbot Andrew" To: rsgb_lf_group@blacksheep.org Date: Tue, 10 Feb 2004 15:56:53 -0000 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2657.72) Subject: RE: LF: Timing GPS Content-Type: text/html; charset=windows-1252 X-Spam-Checker-Version: SpamAssassin 2.60 (1.212-2003-09-23-exp) on post.thorcom.com X-Spam-Status: No, hits=0.6 required=5.0 tests=HTML_20_30,HTML_FONTCOLOR_BLUE,HTML_MESSAGE autolearn=no version=2.60 X-SA-Exim-Scanned: Yes Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-PN-SPAMFiltered: yes X-Spam-Rating: 1 Content-transfer-encoding: 8bit

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
"The Information contained in this E-Mail and any subsequent correspondence"
"is private and is intended solely for the intended recipient(s)."
"For those other than the recipient any disclosure, copying, distribution, "
"or any action taken or omitted to be taken in reliance on such information is"
"prohibited and may be unlawful."