Return-Path: Received: (qmail 4354 invoked from network); 21 Feb 1999 21:02:32 -0000 Received: from magnet.plus.net.uk (HELO magnet.force9.net) (195.166.128.26) by medusa.plus.net.uk with SMTP; 21 Feb 1999 21:02:32 -0000 Received: (qmail 12892 invoked from network); 21 Feb 1999 21:03:22 -0000 Received: from post.thorcom.com (194.75.130.70) by magnet.plus.net.uk with SMTP; 21 Feb 1999 21:03:22 -0000 Received: from troy.blacksheep.org ([194.75.183.50] ident=root) by post.thorcom.com with esmtp (Exim 2.04 #3) id 10Ef6A-0006Wj-00; Sun, 21 Feb 1999 20:03:30 +0000 Received: (from root@localhost) by troy.blacksheep.org (8.6.12/8.6.12) id PAA01401 for rsgb_lf_group-outgoing; Sat, 20 Feb 1999 15:44:41 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 PAA01315 for ; Sat, 20 Feb 1999 15:41:40 GMT Received: from smtp1.xs4all.nl ([194.109.6.51]) by post.thorcom.com with esmtp (Exim 2.04 #3) id 10EB3s-0004es-00 for rsgb_lf_group@blacksheep.org; Sat, 20 Feb 1999 11:59:09 +0000 Received: from PC_misan.xs4all.nl (dc2-isdn2115.dial.xs4all.nl [194.109.156.67]) by smtp1.xs4all.nl (8.8.8/8.8.8) with SMTP id MAA14731; Sat, 20 Feb 1999 12:55:19 +0100 (CET) X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Message-ID: Priority: Normal X-MSMail-Priority: Normal X-Priority: 3 To: g3ldo@zetnet.co.uk Cc: rsgb_lf_group@blacksheep.org MIME-Version: 1.0 From: "M. Sanders" Subject: RE:LF: Re LF Xtal/mixer Exciters Date: Sat, 20 Feb 99 14:20:55 PST Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org Dear OM Peter, G3LDO, I also had bad results with VXO drift both in single X-tal and in mixed settings. I found out that the old big type X-tals in the range between 5 and 9 MHZ are most suitable for use in VXO's. These x-tals give a tuning range well over a 100kC's where the small type X-tals will not tune over a range of more than 30-40kC's The coil in series with te X-tal can play tricks as far as stability is concerned. This can be observed by putting your finger near the inductor. I found out that when the VXO does not return rapidly to its original frequency i had constructed a VFO instead. I had better results when two or more inductors (range at least 1:10 in uH) are put in series, this also limits the influence of paracitic capacitance in the inductors. An other test i found out is to warm one of the x-tals with a finger and observe the drift back to the original frequency when 'cooling off'. When the original frequency is reached i am sure the X-tals have the main influence on the osc illating frequency. An other point a observed is the value to be used for the capactors dividing the voltalge in the collpits should be carefully designed. To mutch amplification makes the oscilator easy to start with a rock-solid frequency. To little amplification will not allow the circuit to oscilate at all. Sometimes a extra buffer/amplifier stage is needed to make sure the mixer works better but this does not influence stability. Good luck on LF and best 73's Mike, PA3BSH Hoogeveen, The Netherlands e-mail also to