Return-Path: Received: (qmail 74928 invoked from network); 26 Sep 2004 22:47:34 -0000 Received: from unknown (HELO ptb-spamcore02.plus.net) (192.168.71.3) by ptb-mailstore01.plus.net with SMTP; 26 Sep 2004 22:47:34 -0000 Received: from mailnull by ptb-spamcore02.plus.net with spamcore-l-b (Exim 4.32; FreeBSD) id 1CBhs9-000Avg-Pa for dave@picks.force9.co.uk; Sun, 26 Sep 2004 23:52:02 +0100 Received: from [192.168.67.3] (helo=ptb-mxcore03.plus.net) by ptb-spamcore02.plus.net with esmtp (Exim 4.32; FreeBSD) id 1CBhs9-000Avd-Me for dave@picks.force9.co.uk; Sun, 26 Sep 2004 23:52:01 +0100 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore03.plus.net with esmtp (Exim) id 1CBhnp-000FHl-WB for dave@picks.force9.co.uk; Sun, 26 Sep 2004 23:47:34 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1CBhnQ-0001wc-Av for rs_out_1@blacksheep.org; Sun, 26 Sep 2004 23:47:08 +0100 Received: from [193.82.116.30] (helo=relay.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1CBhnP-0001wT-U2 for rsgb_lf_group@blacksheep.org; Sun, 26 Sep 2004 23:47:07 +0100 Received: from smtp801.mail.ukl.yahoo.com ([217.12.12.138]) by relay.thorcom.net with smtp (Exim 4.41) id 1CBhnM-0002gc-FE for rsgb_lf_group@blacksheep.org; Sun, 26 Sep 2004 23:47:08 +0100 Received: from unknown (HELO jgtdiynm) (james.moritz@213.122.110.33 with login) by smtp801.mail.ukl.yahoo.com with SMTP; 26 Sep 2004 22:46:58 -0000 Message-ID: <006701c4a41a$a3893640$216e7ad5@jgtdiynm> From: "James Moritz" To: rsgb_lf_group@blacksheep.org Date: Sun, 26 Sep 2004 23:45:25 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.00.2615.200 X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2615.200 X-SPF-Result: relay.thorcom.net: 217.12.12.138 is neither permitted nor denied by domain of btopenworld.com X-Spam-Score: 0.6 (/) X-Spam-Report: autolearn=no,HTML_20_30=0.474,HTML_MESSAGE=0.001,RCVD_IN_SORBS=0.1 Subject: LF: Re: fluted ferrite cores Content-Type: text/html; charset=windows-1252 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_20_30,HTML_MESSAGE 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) Content-transfer-encoding: 8bit

Dear Alan, LF Group,

The fluted ferrite rods are probably "impeder rods" - these are used for induction welding of the seams in metal tubing produced by rolling strip metal. They fit inside the tube at the point where the weld is being made. Their purpose is to force the induced current to flow through the weld, rather than around the circumference of the tube; there is a fairly good description at:

http://www.impeder.com/Efficiency/efficiency.html

The purose of the flutes is to allow the circulation of cooling water, allthough it may also be significant in reducing eddy currents. My old Philips ferrite data book lists these as available in either 3C85 or 3D3 (a somewhat lower permeability ferrite otherwise similar to 3C85). The induction welding application normally operates in the LF/MF range at the 10s of kW level - potentially these might be useful in an LF TX loading coil application, if a coil using them can be made with high enough Q...

Cheers, Jim Moritz

73 de M0BMU