Return-Path: Received: (qmail 8717 invoked from network); 19 Nov 2004 14:20:24 -0000 Received: from unknown (HELO ptb-spamcore01.plus.net) (192.168.71.1) by ptb-mailstore02.plus.net with SMTP; 19 Nov 2004 14:20:24 -0000 Received: from mailnull by ptb-spamcore01.plus.net with spamcore-l-b (Exim 4.32; FreeBSD) id 1CV9u7-0007ha-3P for dave@picks.force9.co.uk; Fri, 19 Nov 2004 14:38:27 +0000 Received: from [192.168.67.1] (helo=ptb-mxcore01.plus.net) by ptb-spamcore01.plus.net with esmtp (Exim 4.32; FreeBSD) id 1CV9u6-0007hV-SB for dave@picks.force9.co.uk; Fri, 19 Nov 2004 14:38:26 +0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore01.plus.net with esmtp (Exim 4.30; FreeBSD) id 1CV9cc-0007qF-P9 for dave@picks.force9.co.uk; Fri, 19 Nov 2004 14:20:22 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1CV9cN-00040T-Kh for rs_out_1@blacksheep.org; Fri, 19 Nov 2004 14:20:07 +0000 Received: from [193.82.116.30] (helo=relay.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1CV9cN-00040K-A3 for rsgb_lf_group@blacksheep.org; Fri, 19 Nov 2004 14:20:07 +0000 Received: from mailout.zetnet.co.uk ([194.247.47.231]) by relay.thorcom.net with esmtp (Exim 4.41) id 1CV9cJ-0008AN-Gg for rsgb_lf_group@blacksheep.org; Fri, 19 Nov 2004 14:20:07 +0000 Received: from irwell.zetnet.co.uk ([194.247.47.48] helo=zetnet.co.uk) by mailout.zetnet.co.uk with esmtp (Exim 3.36 #1 (Debian)) id 1CV9cI-0003Ng-00 for ; Fri, 19 Nov 2004 14:20:02 +0000 Received: from john-b5a82ea1a4 (bts-0323.dialup.zetnet.co.uk [194.247.49.67]) by zetnet.co.uk (8.12.11/8.12.11/Debian-5) with ESMTP id iAJEJldF032367 for ; Fri, 19 Nov 2004 14:20:00 GMT Message-ID: <200411191419510430.03BFEEA7@mail.zetnet.co.uk> In-Reply-To: <01C4CE0F.A626D2D0.actalbot@southsurf.com> References: <01C4CE0F.A626D2D0.actalbot@southsurf.com> X-Mailer: Courier 3.50.00.09.1098 (http://www.rosecitysoftware.com) (K) Date: Fri, 19 Nov 2004 14:19:51 +0000 From: "John Rabson" To: rsgb_lf_group@blacksheep.org Mime-Version: 1.0 X-SPF-Result: relay.thorcom.net: 194.247.47.231 is neither permitted nor denied by domain of zetnet.co.uk X-Spam-Score: 0.1 (/) X-Spam-Report: autolearn=no,RCVD_IN_SORBS=0.1 Subject: Re[2]: LF: Loading Coils 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) On 19/11/2004 at 08:13 Andy wrote: >When it comes to calculations, the most useful ability is not to be able >to >caculate it exactly, caculator or no, but to quickly be able to estimate a >ball >park answer or approximation. > >Who needs to know that 22uH at 137kHz has 18.93 ohms reactance. > >Its quicker to think " a bit more than 20 times a bit less than 0.14, >times > 6-and-a-bit >... is 2.8 times 6-and-a-bit , so call it 18 ohms" > >And they don't teach that in schools - and never have done, to my >knowledge! > >Andy G4JNT I seem to recall a telecommunications professor (Ken Cattermole?) who expected his MSc students at least to have a feel for whether a result was of the right order of magnitude. John G3PAI