Return-Path: Received: (qmail 2400 invoked from network); 5 Aug 2002 15:37:15 -0000 Content-Transfer-Encoding: 8bit Received: from murphys.services.quay.plus.net (212.159.14.225) by mailstore with SMTP; 5 Aug 2002 15:37:15 -0000 X-Priority: 3 X-MSMail-Priority: Normal Received: (qmail 18622 invoked from network); 5 Aug 2002 15:37:23 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from post.thorcom.com (193.82.116.70) by murphys.services.quay.plus.net with SMTP; 5 Aug 2002 15:37:23 -0000 X-SQ: A Received: from majordom by post.thorcom.com with local (Exim 3.33 #2) id 17blR0-000701-00 for rsgb_lf_group-outgoing@blacksheep.org; Mon, 05 Aug 2002 18:14:22 +0100 Received: from relay.dera.gov.uk ([192.5.29.49]) by post.thorcom.com with smtp (Exim 3.33 #2) id 17blQy-0006zt-00 for rsgb_lf_group@blacksheep.org; Mon, 05 Aug 2002 18:14:20 +0100 Received: (qmail 20703 invoked from network); 5 Aug 2002 16:22:47 +0100 Received: from butterfly.mod.uk (HELO warlock.dstl.gov.uk) (192.5.29.10) by relay.dera.gov.uk with SMTP; 5 Aug 2002 16:22:47 +0100 Message-ID: <7D653C9C42F5D411A27C00508BF8803DCB9B63@mail.dstl.gov.uk> From: "Talbot Andrew" To: "LF Group \(E-mail\)" Subject: LF: Confused over Jason coding Date: Mon, 5 Aug 2002 16:22:16 +0100 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2653.19) 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: Must have missed something, but in looking at the coding scheme for the frequency shifts in Jason (as a preliminary to writing some PIC code to drive a DDS chip for a beacon) I came across a snag. The 64 characters are coded 4 bits at a time (allowing for the MSB identifier) as 16 frequency shifts. OK so far, 16 shifts = 4 bits. But, what happens if it is impossible to get more than 8 bits of shift? For instance, say the frequency from the last character ended up at exactly midway - frequency 8. Then it is impossible to code any value greater than 8 without going outside the defined frequency limits. I'm sure this was all explained last year when the mode was being developed but can't find any reference to it now. And the Tech Notes that come with V0.94 don't cover this aspect. A thought has just occurred while writing this - does the direction of frequency shift matter, which can then be taken modulo 16, giving 16 possible shifts from 17 tones? Which means the sideband in use is sensitive. Have I answered my own question ? Andy G4JNT "This e-mail is intended for the recipient only. If you are not the intended recipient you must not use, disclose, distribute, copy, print, or rely upon this e-mail. If an addressing or transmission error has misdirected this e-mail, please notify the author by replying to this e-mail." "Recipients should note that all e-mail traffic on MOD systems is subject to monitoring and auditing."