Return-Path: Received: (qmail 99567 invoked from network); 24 Nov 2004 17:58:47 -0000 Received: from unknown (HELO ptb-spamcore02.plus.net) (192.168.71.3) by ptb-mailstore01.plus.net with SMTP; 24 Nov 2004 17:58:47 -0000 Received: from mailnull by ptb-spamcore02.plus.net with spamcore-l-b (Exim 4.32; FreeBSD) id 1CX1Q4-000Gji-J9 for dave@picks.force9.co.uk; Wed, 24 Nov 2004 17:59:09 +0000 Received: from [192.168.67.1] (helo=ptb-mxcore01.plus.net) by ptb-spamcore02.plus.net with esmtp (Exim 4.32; FreeBSD) id 1CX1Q4-000Gje-EY for dave@picks.force9.co.uk; Wed, 24 Nov 2004 17:59:08 +0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore01.plus.net with esmtp (Exim 4.30; FreeBSD) id 1CX1Pi-0003TT-AG for dave@picks.force9.co.uk; Wed, 24 Nov 2004 17:58:46 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1CX1OY-0002jY-4M for rs_out_1@blacksheep.org; Wed, 24 Nov 2004 17:57:34 +0000 Received: from [193.82.116.30] (helo=relay.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1CX1OX-0002jP-OZ for rsgb_lf_group@blacksheep.org; Wed, 24 Nov 2004 17:57:33 +0000 Received: from imo-m22.mx.aol.com ([64.12.137.3]) by relay.thorcom.net with esmtp (Exim 4.41) id 1CX1OU-0005HK-4I for rsgb_lf_group@blacksheep.org; Wed, 24 Nov 2004 17:57:33 +0000 Received: from DL4YHF@aol.com by imo-m22.mx.aol.com (mail_out_v37_r3.8.) id l.100.74d81f6 (3940) for ; Wed, 24 Nov 2004 12:57:15 -0500 (EST) From: DL4YHF@aol.com Message-ID: <100.74d81f6.2ed6257b@aol.com> Date: Wed, 24 Nov 2004 12:57:15 EST To: rsgb_lf_group@blacksheep.org MIME-Version: 1.0 X-Mailer: 8.0 for Windows sub 6104 X-SPF-Result: relay.thorcom.net: domain of aol.com designates 64.12.137.3 as permitted sender X-Spam-Score: 0.7 (/) X-Spam-Report: autolearn=no,HTML_MESSAGE=0.001,HTML_TAG_BALANCE_HTML=0.411,NO_REAL_NAME=0.285 Subject: Re: LF: Linear amplifiers , MSK, and 500kHz Content-Type: text/html; charset=windows-1252 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Status: No, hits=0.7 required=5.0 tests=HTML_MESSAGE, HTML_TAG_BALANCE_HTML,NO_REAL_NAME autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-Spam-Filtered: by PlusNet SpamCORE (v3.00) Content-transfer-encoding: 8bit Hi Alberto,

Will one of the big "pro's" of COFDM -its immunity to multipath and "reflections"- really so important on LF with a very low symbol rate ? - well this is just an initial thought, I don't really know much about COFDM except that it is used in DVB-T (which we don't have in this underdeveloped part of DL yet, hi).

About the peak-to-average ratio (~ crest factor): An analogy to DF6NM's chirped hell (or "fourier SSTV") transmissions came to my mind. To reduce the crest factor, Markus uses a squared phase relationship for all "tones" (alias frequency bins in the IFFT) in a transmitted pixel strip. This is a really large improvement, compared to the classic "concurrent" multi-tone hell (more info available). But I have no clue if a similar principle can be applied to COFDM to reduce the creast factor there (wouldn't be "cOfdm" any longer?) .

Best greetings,

Wolf DL4YHF.