Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-da03.r1000.mx.aol.com (Internet Inbound) with ESMTP id 0513C380000A1; Fri, 6 Jul 2012 03:32:45 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Sn30b-0004Ob-JV for rs_out_1@blacksheep.org; Fri, 06 Jul 2012 08:31:21 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Sn30a-0004OS-OX for rsgb_lf_group@blacksheep.org; Fri, 06 Jul 2012 08:31:20 +0100 Received: from smtp-out21.han.skanova.net ([195.67.226.208]) by relay1.thorcom.net with esmtp (Exim 4.77) (envelope-from ) id 1Sn30Z-0002Jb-4Q for rsgb_lf_group@blacksheep.org; Fri, 06 Jul 2012 08:31:19 +0100 Received: from [127.0.0.1] (217.211.186.120) by smtp-out21.han.skanova.net (8.5.133) (authenticated as u33233109) id 4FD624AF00881387 for rsgb_lf_group@blacksheep.org; Fri, 6 Jul 2012 09:31:17 +0200 Message-ID: <4FF69444.7040603@telia.com> Date: Fri, 06 Jul 2012 09:31:16 +0200 From: "Johan H. Bodin" User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:13.0) Gecko/20120614 Thunderbird/13.0.1 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <7E7DFBB4D102A04DB5ADC88D66628A4A0FAB99CC@ICTS-S-MBX5.luna.kuleuven.be> <1SmrFA-199XcW0@fwd21.t-online.de> <4FF5EB68.9040507@iup.uni-heidelberg.de> <4FF61402.6000703@iup.uni-heidelberg.de> In-Reply-To: X-Spam-Score: -0.7 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has identified this incoming email as possible spam. The original message has been attached to this so you can view it (if it isn't spam) or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: Stefan, Jim is right as always. Ferrite is unusable in VFO inductors. I just wanted to add that Micrometals (== Amidon) Txx-6 has a slightly lower temperature coefficient than Txx-2. I have built successful VFOs operating directly on 7 and 10 MHz with T50-6 cores. After some work, the drift was low enough to go unnoticed in a QRP CW rig. The inductor, and many other components usually have a positive temperature coefficient, the QRG falls as the temp' rises. One trick is to use temperature stable capacitors for most of the tank capacitance, "styroflex" mentioned by Peter is very good if you can find them, and use negative tempco ceramic caps (N750, N1500) for a carefully selected portion of the total capacitance. In todays world of microchips, I find it fun, educational and rewarding to experiment with an analog VFO :-) [...] Content analysis details: (-0.7 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.7 RCVD_IN_DNSWL_LOW RBL: Sender listed at http://www.dnswl.org/, low trust [195.67.226.208 listed in list.dnswl.org] X-Scan-Signature: 87966b345956c8ef3389b993f6a18f4e Subject: Re: LF: RE: Analog oscillators Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: 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-aol-global-disposition: G X-AOL-SCOLL-SCORE: 0:2:364010080:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d404b4ff6949d0e3e X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none Stefan, Jim is right as always. Ferrite is unusable in VFO inductors. I just wanted to add that Micrometals (== Amidon) Txx-6 has a slightly lower temperature coefficient than Txx-2. I have built successful VFOs operating directly on 7 and 10 MHz with T50-6 cores. After some work, the drift was low enough to go unnoticed in a QRP CW rig. The inductor, and many other components usually have a positive temperature coefficient, the QRG falls as the temp' rises. One trick is to use temperature stable capacitors for most of the tank capacitance, "styroflex" mentioned by Peter is very good if you can find them, and use negative tempco ceramic caps (N750, N1500) for a carefully selected portion of the total capacitance. In todays world of microchips, I find it fun, educational and rewarding to experiment with an analog VFO :-) 73 Johan SM6LKM James Moritz wrote: > I suggest using a Txx-2 iron dust core insted of the -43 ferrite.