Return-Path: Received: (qmail 96579 invoked from network); 19 Nov 2004 14:16:02 -0000 Received: from unknown (HELO ptb-spamcore01.plus.net) (192.168.71.1) by ptb-mailstore02.plus.net with SMTP; 19 Nov 2004 14:16:02 -0000 Received: from mailnull by ptb-spamcore01.plus.net with spamcore-l-b (Exim 4.32; FreeBSD) id 1CV9pq-0006mV-I6 for dave@picks.force9.co.uk; Fri, 19 Nov 2004 14:34:06 +0000 Received: from [192.168.67.2] (helo=ptb-mxcore02.plus.net) by ptb-spamcore01.plus.net with esmtp (Exim 4.32; FreeBSD) id 1CV9pq-0006mS-Ek for dave@picks.force9.co.uk; Fri, 19 Nov 2004 14:34:02 +0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore02.plus.net with esmtp (Exim) id 1CV9YM-000N7L-Ec for dave@picks.force9.co.uk; Fri, 19 Nov 2004 14:15:58 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1CV9Y4-0003ur-Ht for rs_out_1@blacksheep.org; Fri, 19 Nov 2004 14:15:40 +0000 Received: from [193.82.116.30] (helo=relay.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1CV9Y4-0003ui-7L for rsgb_lf_group@blacksheep.org; Fri, 19 Nov 2004 14:15:40 +0000 Received: from anchor-post-33.mail.demon.net ([194.217.242.91]) by relay.thorcom.net with esmtp (Exim 4.41) id 1CV9Xz-00088u-63 for rsgb_lf_group@blacksheep.org; Fri, 19 Nov 2004 14:15:40 +0000 Received: from pickmere.demon.co.uk ([158.152.117.143]) by anchor-post-33.mail.demon.net with esmtp (Exim 4.42) id 1CV9Xw-000EH0-Af for rsgb_lf_group@blacksheep.org; Fri, 19 Nov 2004 14:15:34 +0000 Message-ID: Date: Fri, 19 Nov 2004 12:03:04 +0000 To: rsgb_lf_group@blacksheep.org From: "M. J. Powell" References: <01C4CE0F.A626D2D0.actalbot@southsurf.com> In-Reply-To: <01C4CE0F.A626D2D0.actalbot@southsurf.com> MIME-Version: 1.0 User-Agent: Turnpike/6.01-S () X-SPF-Result: relay.thorcom.net: 194.217.242.91 is neither permitted nor denied by domain of pickmere.demon.co.uk X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=no, Subject: Re: LF: Loading Coils Content-Type: text/plain; charset=us-ascii; format=flowed 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) Content-transfer-encoding: 8bit In message <01C4CE0F.A626D2D0.actalbot@southsurf.com>, Andy writes >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! They did in my school, as a check on the calculation. But I went to school during the war, and was taught by teachers who had retired before the war and came back to replace those called up. WW II, of course! Mike -- M.J.Powell