Return-Path: Received: (qmail 9865 invoked from network); 25 Feb 2000 14:02:24 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by bells.core.plus.net.uk with SMTP; 25 Feb 2000 14:02:24 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.02 #1) id 12OLDY-0008CA-00 for rsgb_lf_group-outgoing@blacksheep.org; Fri, 25 Feb 2000 13:55:40 +0000 Received: from bob.dera.gov.uk ([192.5.29.90]) by post.thorcom.com with esmtp (Exim 3.02 #1) id 12OLDT-0008C2-00 for rsgb_lf_group@blacksheep.org; Fri, 25 Feb 2000 13:55:36 +0000 Content-Transfer-Encoding: 8bit Received: by bob.dera.gov.uk; (8.8.8/1.3/10May95) id NAA22463; Fri, 25 Feb 2000 13:57:05 GMT Received: (qmail 27433 invoked from network); 25 Feb 2000 14:52:26 -0000 X-Priority: 3 X-MSMail-Priority: Normal Received: from gauntlet.mail.dera.gov.uk (172.16.9.10) by baton.dera.gov.uk with SMTP; 25 Feb 2000 14:52:26 -0000 Received: by gauntlet.mail.dera.gov.uk; id NAA13126; Fri, 25 Feb 2000 13:49:08 GMT Received: from unknown(146.80.11.40) by gauntlet.mail.dera.gov.uk via smap (3.2) id xma013052; Fri, 25 Feb 00 13:49:01 GMT X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from frn-gold-1.dera.gov.uk (unverified) by mailguard.dera.gov.uk (Content Technologies SMTPRS 2.0.15) with ESMTP id for ; Fri, 25 Feb 2000 13:56:05 +0000 Received: by FRN-GOLD-1 with Internet Mail Service (5.0.1460.8) id <1K87GJ6R>; Fri, 25 Feb 2000 13:53:33 -0000 Message-ID: <3617AC3245C2D1118A840000F805359C01206E6C@PDW-MERCURY-1> From: "Talbot Andrew" To: "'LF Group'" Subject: LF: PSK08 Tests Date: Fri, 25 Feb 2000 13:53:30 -0000 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.0.1460.8) Content-Type: text/plain; charset=iso-8859-1; format=flowed Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: Now I know a few copies of PSK08 are out there I'll transmit this evening around 2000z. Frequency will be 137.500 +/- 0.5 Hz, chosen after careful consulation with this group :-|) Probably won't listen too much as no one has replied to say they can transmit yet and I know that three of those who have downloaded the code are listeners only. There is another modulation scheme suitable for this band that does allow constant amplitude, and hence highly efficient class D amplifiers. That is Continuous Phase Modulation (CPM), of which Minimum Shift Keying is an extreme example. Listen to the transmission from Rugby on 16kHz or 22.1 kHz for an excellent example of a 100 Baud version of MSK. CPM is a very processor and memory intensive mode hence it is only now becoming popular, but at the speeds used at LF my feeling is that a PC could cope even if a 56002 EVM does not have the necessary memory capacity. CPM is theoretically a few dB better than PSK in S/N terms, and in fact with the right coding is said to be able to get to within 0.7db of the Shannon limit. Take this together with the constant envelope waveform and it could prove very exciting for very weak signal LF dxing. If anyone reading this has a more intimate knowledge of CPM please get in touch. As far as I 'm concerned its all squiggles in a text book at the moment, and as for turning these into DSP code.... Andy G4JNT Now ignore what follows :-|( -- 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.