Return-Path: Received: (qmail 15094 invoked from network); 3 Jan 2002 08:54:02 -0000 Received: from unknown (HELO murphys-inbound.services.quay.plus.net) (212.159.14.225) by excalibur.plus.net with SMTP; 3 Jan 2002 08:54:02 -0000 Received: (qmail 2021 invoked from network); 3 Jan 2002 08:53:59 -0000 X-Priority: 3 X-MSMail-Priority: Normal Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by murphys.services.quay.plus.net with SMTP; 3 Jan 2002 08:53:59 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from majordom by post.thorcom.com with local (Exim 3.33 #2) id 16M3Wz-0000YF-00 for rsgb_lf_group-outgoing@blacksheep.org; Thu, 03 Jan 2002 08:47:21 +0000 Received: from bob.dera.gov.uk ([192.5.29.90]) by post.thorcom.com with esmtp (Exim 3.33 #2) id 16M3Wy-0000YA-00 for rsgb_lf_group@blacksheep.org; Thu, 03 Jan 2002 08:47:20 +0000 Received: by bob.dera.gov.uk; (8.8.8/1.3/10May95) id IAA09058; Thu, 3 Jan 2002 08:55:55 GMT Received: (qmail 2282 invoked from network); 3 Jan 2002 09:35:56 -0000 Received: from gauntlet.mail.dstl.gov.uk (192.168.9.10) by baton.dstl.gov.uk with SMTP; 3 Jan 2002 09:35:56 -0000 Received: by gauntlet.mail.dstl.gov.uk; id JAA07728; Thu, 3 Jan 2002 09:06:29 GMT Received: from unknown(172.17.128.171) by gauntlet.mail.dstl.gov.uk via smap (3.2) id xma007713; Thu, 3 Jan 02 09:06:27 GMT Received: from FRN-MAIL-R3.dstl.gov.uk (unverified) by mailguard.dstl.gov.uk (Content Technologies SMTPRS 4.1.5) with ESMTP id for ; Thu, 3 Jan 2002 08:52:24 +0000 Received: by frn-mail-r3.dstl.gov.uk with Internet Mail Service (5.5.2650.21) id ; Thu, 3 Jan 2002 08:46:20 -0000 Message-ID: <7D653C9C42F5D411A27C00508BF8803D55C682@pdw-mail-r1.dstl.gov.uk> From: "Talbot Andrew" To: rsgb_lf_group@blacksheep.org Subject: LF: Phase Sensitive Waterfall Date: Thu, 3 Jan 2002 08:46:17 -0000 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2650.21) Content-Type: text/html; charset=windows-1252 Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: Content-transfer-encoding: 8bit

I think the soundcard stability is too poor to be able to rely on for phase measurements. Instead, how about a phase meter that works by comparing the phase of a signal on the left channel input with a supplied reference tone on the right channel. Then, all that anyone need do is construct a stable oscillator and divider to generate, say, a 1kHz, tone.

I regularly use a phase meter based on the 56002EVM. The DSP card performs the digitisation, downconversion and decimation, outputting I/Q samples at user selectable data rates from 800 Hz right down to 1.95 Hz (8000 / 4096) via the COM port to a PC for further analysis. In my case the EVM sampling clock is stabilised so there is no need for a comparison tone to measure phase.

A waterfall plot of phase would be a wonderful and easy way to get a few more dB of sensitivity out of slow signalling over power detection methods.. Even if the frequency stability is insufficient to maintain phase over a symbol period, it should still be easy to spot the data transitions by eye. The only problem then would be resolving the 0/180 degree ambiguity.

Andy G4JNT

Alan - in fact I have been playing with a "phase sensitive waterfall display" which Markus DF6NM suggested over half a year ago. Indeed, the result of the FFT calculation carries the amplitude and phase, but it's not easy to interpret the phase values and putting subsequent FFT results together (all I got up to now is a very colorfull display which looks like "moiré effect" on a TV screen. But with a bit of inspiration, there will be more soon... :-)





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