Return-Path: Received: (qmail 23313 invoked from network); 19 Feb 1999 13:44:45 -0000 Received: from magnet.plus.net.uk (HELO magnet.force9.net) (195.166.128.26) by medusa.plus.net.uk with SMTP; 19 Feb 1999 13:44:45 -0000 Received: (qmail 17223 invoked from network); 19 Feb 1999 13:45:20 -0000 Received: from post.thorcom.com (194.75.130.70) by magnet.plus.net.uk with SMTP; 19 Feb 1999 13:45:20 -0000 Received: from troy.blacksheep.org ([194.75.183.50] ident=root) by post.thorcom.com with esmtp (Exim 2.04 #3) id 10Dq6S-0004ni-01; Fri, 19 Feb 1999 13:36:25 +0000 X-Priority: 3 X-MSMail-Priority: Normal Received: (from root@localhost) by troy.blacksheep.org (8.6.12/8.6.12) id NAA24561 for rsgb_lf_group-outgoing; Fri, 19 Feb 1999 13:18:54 GMT Received: from post.thorcom.com (root@post.unica.co.uk [194.75.183.70]) by troy.blacksheep.org (8.6.12/8.6.12) with ESMTP id NAA24479 for ; Fri, 19 Feb 1999 13:17:46 GMT X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from irwell.zetnet.co.uk ([194.247.47.48] ident=root) by post.thorcom.com with esmtp (Exim 2.04 #3) id 10DmqP-00080O-00 for rsgb_lf_group@blacksheep.org; Fri, 19 Feb 1999 10:07:37 +0000 Received: from central.zetnet.co.uk (central.zetnet.co.uk [194.247.47.20]) by irwell.zetnet.co.uk (8.8.7/8.8.5) with SMTP id KAA12191 for ; Fri, 19 Feb 1999 10:03:44 GMT X-ZSender: g3ldo@zetnet.co.uk Message-ID: <1999021910062568199@zetnet.co.uk> Date: Fri, 19 Feb 1999 10:06:25 GMT To: rsgb_lf_group@blacksheep.org From: "Peter Dodd" X-Mailer: ZIMACS Version 1.20c 10000836 Subject: LF: Re LF Xtal/mixer Exciters Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org Content-type: text/plain; charset=windows-1252; format=flowed MIME-Version: 1.0 Content-transfer-encoding: 8bit CRYSTAL MIXER EXCITER FOR 137KHZ All my attempts to construct any sort of VFO/synthesiser/divider have ended in failure. I am not sure why I have such a reliable failure rate with digital circuits - I strongly suspect incompetence. It is not the case that my amplifiers oscillate and my oscillators don't. I seem to be able to make ugly construction RF and AF circuits that work first time so I was looking a solution that did not involve digital circuits. >From crystals box I found two crystals on 10489.37 and 10355.0 kHz respectively. I built two FET Colpits oscillators, firstly with a variable capacitor across the lower frequency oscillator crystal but then found that it worked best (even output across the frequency range) with the variable capacitor in series higher oscillator crystal. While trying to decided on a suitable mixer/filter I saw this e-mail from Peter DF3LP who described a very similar exciter. Peter kindly sent me a copy of his circuit (which uses 5MHz crystals) , which gave me enough ideas to complete the exciter. Apparently the first circuit of this type (that I am aware of) was built by DJ1ZB. The main attraction of this circuit is that if both oscillators are built in the same enclosure with identical components the output frequency is held constant because any drift in one oscillator is compensated for by an equivalent drift in the other. My circuit is made from junk box components and the measured drift was 137.6530kHz to start and 137.6524kHz after 3 hours. In my last e-mail I described a SCW QSO with DJ8WL (using the above exciter I might add) whos name I gave as Geri! Sorry Peter. -- Regards, Peter, G3LDO