Return-Path: Received: (qmail 12030 invoked from network); 14 Jan 2005 14:21:02 -0000 Received: from unknown (HELO ptb-spamcore02.plus.net) (192.168.71.3) by ptb-mailstore02.plus.net with SMTP; 14 Jan 2005 14:21:02 -0000 Received: from mailnull by ptb-spamcore02.plus.net with spamcore-l-b (Exim 4.32; FreeBSD) id 1CpSFg-000ENF-Go for dave@picks.force9.co.uk; Fri, 14 Jan 2005 14:16:42 +0000 Received: from [192.168.67.2] (helo=ptb-mxcore02.plus.net) by ptb-spamcore02.plus.net with esmtp (Exim 4.32; FreeBSD) id 1CpSFf-000EMm-At for dave@picks.force9.co.uk; Fri, 14 Jan 2005 14:16:35 +0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore02.plus.net with esmtp (Exim) id 1CpSJn-00052h-Dd for dave@picks.force9.co.uk; Fri, 14 Jan 2005 14:20:51 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1CpSJ3-0005iM-PW for rs_out_1@blacksheep.org; Fri, 14 Jan 2005 14:20:05 +0000 Received: from [193.82.116.30] (helo=relay.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1CpSJ3-0005iD-Dp for rsgb_lf_group@blacksheep.org; Fri, 14 Jan 2005 14:20:05 +0000 Received: from smtpout03-04.mesa1.secureserver.net ([64.202.165.74]) by relay.thorcom.net with smtp (Exim 4.43) id 1CpSJ0-0007eO-PU for rsgb_lf_group@blacksheep.org; Fri, 14 Jan 2005 14:20:05 +0000 Received: (qmail 16025 invoked from network); 14 Jan 2005 14:19:47 -0000 Received: from unknown (208.37.242.34) by smtpout03-04.mesa1.secureserver.net (64.202.165.74) with ESMTP; 14 Jan 2005 14:19:47 -0000 Message-ID: <000801c4fa44$55fe0f10$3801a8c0@JKA> From: "John Andrews" To: rsgb_lf_group@blacksheep.org References: Date: Fri, 14 Jan 2005 09:21:26 -0500 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1437 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1441 X-SPF-Result: relay.thorcom.net: 64.202.165.74 is neither permitted nor denied by domain of w1tag.com X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=failed,none Subject: Re: LF: Simple image-cancelling exciter for digimodes Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com 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-Spam-Filtered: by PlusNet SpamCORE (v3.00) Jan-Martin, >very interesting, and it is still allowed to use an additional notch filter, or did I misundertand?< At this point, no extra filtering should be required. The quadrature outputs from the sound card are run through a TL074 to provide 0, 90, 180 and 270 degree audio sources (the 180 and 270 are just inverted from the 0 and 90). That is applied to the four switches in the 74HC4066. The switches are driven from a 4X signal that goes through a ring counter and decoder to provide 0, 90, 180 and 270 degree outputs. The outputs of the switches are summed into an opamp that provides 0 dBm into 50 ohms. The only conventional filter is a simple half-wave filter at the 50 ohm output. I'll have a schematic this weekend, but there are still a few problems to solve. John Andrews