Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-da06.r1000.mx.aol.com (Internet Inbound) with ESMTP id 45A2338000096; Wed, 11 Jul 2012 05:20:26 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Sot4c-0006nq-Q6 for rs_out_1@blacksheep.org; Wed, 11 Jul 2012 10:19:06 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Sot4c-0006nh-7a for rsgb_lf_group@blacksheep.org; Wed, 11 Jul 2012 10:19:06 +0100 Received: from mtaout01-winn.ispmail.ntl.com ([81.103.221.47]) by relay1.thorcom.net with esmtp (Exim 4.77) (envelope-from ) id 1Sot4a-0002DT-Na for rsgb_lf_group@blacksheep.org; Wed, 11 Jul 2012 10:19:05 +0100 Received: from aamtaout04-winn.ispmail.ntl.com ([81.103.221.35]) by mtaout01-winn.ispmail.ntl.com (InterMail vM.7.08.04.00 201-2186-134-20080326) with ESMTP id <20120711091903.OBPN3118.mtaout01-winn.ispmail.ntl.com@aamtaout04-winn.ispmail.ntl.com>; Wed, 11 Jul 2012 10:19:03 +0100 Received: from [192.168.2.2] (really [82.5.252.56]) by aamtaout04-winn.ispmail.ntl.com (InterMail vG.3.00.04.00 201-2196-133-20080908) with ESMTP id <20120711091903.GUKF16631.aamtaout04-winn.ispmail.ntl.com@[192.168.2.2]>; Wed, 11 Jul 2012 10:19:03 +0100 From: "Mike Dennison" To: rsgb_lf_group@blacksheep.org, rsgb_lf_group@yahoogroups.co.uk Date: Wed, 11 Jul 2012 10:18:59 +0100 MIME-Version: 1.0 Message-ID: <4FFD5313.6103.333D978@mike.dennison.ntlworld.com> In-reply-to: References: , <4FFC3518.1030405@xs4all.nl>, X-mailer: Pegasus Mail for Windows (4.41) Content-description: Mail message body X-Cloudmark-Analysis: v=1.1 cv=VdgNzmuW7WWMT1Qny0gF8TcKsDP1s+e8NM1Fi0y20Rs= c=1 sm=0 a=uObrxnre4hsA:10 a=9YlaCzn6_68A:10 a=kj9zAlcOel0A:10 a=QZam-5MpAAAA:8 a=6_K2sCJmpiDQip9BzWQA:9 a=CjuIK1q_8ugA:10 a=E2EK3x6scgcA:10 a=HpAAvcLHHh0Zw7uRqdWCyQ==:117 X-Spam-Score: -0.0 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has identified this incoming email as possible spam. The original message has been attached to this so you can view it (if it isn't spam) or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: > Narrow IF filters are not desirable and reduce the > performance of the demodulator , better simply use SSB filter > GL ..73 -G.. Graham, Why is that the case? What does the considerable extra bandwidth achieve? Is the SSB bandwidth optimal, or would it be even better with 10kHz bandwidth, or 100kHz?. Why is 3kHz better than perhaps 1kHz or 2kHz? [...] Content analysis details: (-0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [81.103.221.47 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record X-Scan-Signature: 0a4643e586472c13187d293ec5d096c2 Subject: Re: LF: OPERA Question Content-type: text/plain; charset=US-ASCII Content-transfer-encoding: 7BIT X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=none 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-aol-global-disposition: G X-AOL-SCOLL-SCORE: 0:2:265390032:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d404e4ffd455a7160 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none > Narrow IF filters are not desirable and reduce the > performance of the demodulator , better simply use SSB filter > GL ..73 -G.. Graham, Why is that the case? What does the considerable extra bandwidth achieve? Is the SSB bandwidth optimal, or would it be even better with 10kHz bandwidth, or 100kHz?. Why is 3kHz better than perhaps 1kHz or 2kHz? At first glance it appears crazy to let in all sorts of adjacent channel QRM (the bandwidth is more than ten times the size of the entire Opera window) when using a mode that occupies a fraction of 1Hz. Is it simply that the 1.7kHz Tx tone is high enough for the SSB filter to kill its harmonics, and on receive it is difficult to get a 1.7kHz tone out of a CW filter, even with passband shifting. Am I missing something? 73 de Mike, G3XDV g3xdv.blogspot.co.uk ================