Return-Path: Received: (qmail 33510 invoked from network); 13 Jul 2004 10:29:30 -0000 Received: from unknown (HELO ptb-spamcore01.plus.net) (192.168.71.1) by ptb-mailstore01.plus.net with SMTP; 13 Jul 2004 10:29:30 -0000 Received: from [192.168.67.1] (helo=ptb-mxcore01.plus.net) by ptb-spamcore01.plus.net with esmtp (Exim 4.32; FreeBSD) id 1BkKYQ-000HcK-JC for dave@picks.force9.co.uk; Tue, 13 Jul 2004 11:30:30 +0100 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore01.plus.net with esmtp (Exim 4.30; FreeBSD) id 1BkKXP-000As5-OK for dave@picks.force9.co.uk; Tue, 13 Jul 2004 10:29:27 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1BkKWq-0007op-KL for rs_out_1@blacksheep.org; Tue, 13 Jul 2004 11:28:52 +0100 Received: from [193.82.116.30] (helo=relay.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1BkKWq-0007og-8R for rsgb_lf_group@blacksheep.org; Tue, 13 Jul 2004 11:28:52 +0100 Received: from hestia.herts.ac.uk ([147.197.200.9]) by relay.thorcom.net with esmtp (Exim 4.34) id 1BkKWm-0007z4-SU for rsgb_lf_group@blacksheep.org; Tue, 13 Jul 2004 11:28:52 +0100 Received: from altair ([147.197.200.45] helo=altair.herts.ac.uk) by hestia.herts.ac.uk with esmtp (Exim 3.22 #1) id 1BkKWL-00045F-00 for rsgb_lf_group@blacksheep.org; Tue, 13 Jul 2004 11:28:21 +0100 Received: from [147.197.164.230] (helo=JamesMorrits) by altair.herts.ac.uk with esmtp (Exim 3.36 #1) id 1BkKWK-0003vg-00 for rsgb_lf_group@blacksheep.org; Tue, 13 Jul 2004 11:28:20 +0100 From: "James Moritz" To: rsgb_lf_group@blacksheep.org Date: Tue, 13 Jul 2004 11:28:20 +0100 Message-ID: MIME-Version: 1.0 X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.4510 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1409 X-UH-MailScanner: No Virus detected X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=no, Subject: LF: RE: Re receivers again 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) Dear Mike, LF Group, As regards older receivers, I have tried the HRO, CR100 and AR88LF on 136kHz - they all suffer the problem of poor skirt selectivity, which, combined with the lack of a proper product detector, gives problems with adjacent signals like DCF39. The sensitivity is good however; the input impedance of this type of RX is designed to be quite high on the LF bands, so a wire antenna can be connected directly without additional tuning components. If one were to fit a modern IF filter, the performance would be quite good. I also have had good results using a Telefunken ELK639 - this is an early solid-state marine receiver, with two separate gang-tuned front ends which tune 9.8kHz - 30MHz. This has good mechanical filters, and also works well with a directly connected antenna. Still hasn't got a product detector though... Mostly I use the Racal RA1792, which gives good performance at 136k, and is usable to below 15kHz. The only problem is that the IF filters are not as good as current receivers, so there is a noticeable, although not serious, leakage of adjacent strong signals. The front panel controls are a bit idiosyncratic too. The older RA1772 is similar. These receivers have the advantage of very good frequency stability due to the internal crystal oven, and the facility to connect external frequency standards, e.g. GPS-derrived. Also, the RF and IF signal paths are easy to get at, so I would recommend these for the more experimentally minded. Cheers, Jim Moritz 73 de M0BMU