Return-Path: Received: (qmail 64744 invoked from network); 18 Sep 2004 08:39:05 -0000 Received: from unknown (HELO ptb-spamcore01.plus.net) (192.168.71.1) by ptb-mailstore01.plus.net with SMTP; 18 Sep 2004 08:39:05 -0000 Received: from mailnull by ptb-spamcore01.plus.net with spamcore-l-b (Exim 4.32; FreeBSD) id 1C8at0-000Nwm-MI for dave@picks.force9.co.uk; Sat, 18 Sep 2004 09:48:03 +0100 Received: from [192.168.67.3] (helo=ptb-mxcore03.plus.net) by ptb-spamcore01.plus.net with esmtp (Exim 4.32; FreeBSD) id 1C8at0-000Nwj-Jk for dave@picks.force9.co.uk; Sat, 18 Sep 2004 09:48:02 +0100 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore03.plus.net with esmtp (Exim) id 1C8akK-000JX2-Pc for dave@picks.force9.co.uk; Sat, 18 Sep 2004 09:39:04 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1C8ajR-0002Dt-1P for rs_out_1@blacksheep.org; Sat, 18 Sep 2004 09:38:09 +0100 Received: from [193.82.116.30] (helo=relay.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1C8ajQ-0002Dk-Lq for rsgb_lf_group@blacksheep.org; Sat, 18 Sep 2004 09:38:08 +0100 Received: from cas-mta4-fe.casema.nl ([83.80.1.32] helo=mta.casema.nl) by relay.thorcom.net with esmtp (Exim 4.41) id 1C8ajN-0007tv-4m for rsgb_lf_group@blacksheep.org; Sat, 18 Sep 2004 09:38:08 +0100 Received: from w8k3f0.casema.nl (53556B6D.cable.casema.nl [83.85.107.109]) by cas-mta4.mgmt.casema.nl (iPlanet Messaging Server 5.2 HotFix 1.21 (built Sep 8 2003)) with ESMTP id <0I4800JAMANBIG@cas-mta4.mgmt.casema.nl> for rsgb_lf_group@blacksheep.org; Sat, 18 Sep 2004 10:38:00 +0200 (CEST) Date: Sat, 18 Sep 2004 10:44:27 +0200 From: Dick Rollema X-Sender: dickrollema@casema.nl@mail.casema.nl (Unverified) To: LF-Group Message-id: <6.1.0.6.2.20040918100413.036279c0@mail.casema.nl> MIME-version: 1.0 X-Mailer: QUALCOMM Windows Eudora Version 6.1.0.6 X-SPF-Result: relay.thorcom.net: 83.80.1.32 is neither permitted nor denied by domain of casema.nl X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=no, Subject: LF: SL6440/mixer Content-type: text/plain; charset=us-ascii; 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) To All from PA0SE When I had to decide what type of mixers to use in my new TRX, a doubly balanced passive diode mixer or the SL6440, I chose the latter for the following reasons. 1. The SL6440 amplifies so there is no need for an amplifier between the mixed and the following IF filter. 2. The SL6440 requires very little LO power 3. There is no need for critical terminations of the ports, as is the case with a passive mixer. Both PA0KDF and I found that the LO signal appears very strong in phase at the output pins 3 and 14 of the SL6440 and this signal must be suppressed to enjoy the full large signal capability. I did this by connecting a parallel tuned circuit between the pins with the centre of the coil grounded for RF and connected to 12V. The circuit is tuned to the IF and the IF signal extracted by a link over the coil. I also use a balanced circuit at the input of the mixer. The large signal behaviour of the receiver is very good. Using a 2 x 20 m dipole on 7MHz there is no trace of IM when listening on a winter night. Not even when the 12dB preamplifier is switched on. As a test of course, the amp is not needed below 24MHz. But in this respect the Cohn bandpass filter (bandwidth 180kHz) at the input of the receiver helps as well. The SL6440 is no longer in production, though they can still be found. But if you are going to use one better buy some spares as well. Fortunately they are not very expensive. 73, Dick, PA0SE