Return-Path: Received: (qmail 95444 invoked from network); 19 Nov 2004 01:12:07 -0000 Received: from unknown (HELO ptb-spamcore02.plus.net) (192.168.71.3) by ptb-mailstore02.plus.net with SMTP; 19 Nov 2004 01:12:07 -0000 Received: from mailnull by ptb-spamcore02.plus.net with spamcore-l-b (Exim 4.32; FreeBSD) id 1CUxIe-000F6s-II for dave@picks.force9.co.uk; Fri, 19 Nov 2004 01:10:57 +0000 Received: from [192.168.67.2] (helo=ptb-mxcore02.plus.net) by ptb-spamcore02.plus.net with esmtp (Exim 4.32; FreeBSD) id 1CUxIe-000F6p-C3 for dave@picks.force9.co.uk; Fri, 19 Nov 2004 01:10:56 +0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore02.plus.net with esmtp (Exim) id 1CUxJC-000Mqg-FN for dave@picks.force9.co.uk; Fri, 19 Nov 2004 01:11:30 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1CUxI5-0002IC-8b for rs_out_1@blacksheep.org; Fri, 19 Nov 2004 01:10:21 +0000 Received: from [193.82.116.30] (helo=relay.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1CUxI4-0002I3-Pm for rsgb_lf_group@blacksheep.org; Fri, 19 Nov 2004 01:10:20 +0000 Received: from ms.genesis-technology.com ([63.171.43.8]) by relay.thorcom.net with esmtp (Exim 4.41) id 1CUxI0-0005w8-Pn for rsgb_lf_group@blacksheep.org; Fri, 19 Nov 2004 01:10:20 +0000 Received: from [192.168.0.100] (rev-65.165.20.91.genesiswireless.us [65.165.20.91]) by ms.genesis-technology.com (8.12.9/8.12.9) with ESMTP id iAJ19OkA004128 for ; Thu, 18 Nov 2004 19:09:24 -0600 Message-ID: <419D4887.1040005@genesiswireless.us> Date: Thu, 18 Nov 2004 19:12:39 -0600 From: WE0H Mike User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.7.2) Gecko/20040804 Netscape/7.2 (ax) X-Accept-Language: en-us, en MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <01C4CCB4.3A7963B0.actalbot@southsurf.com> <002401c4cdc7$94613100$80457ad5@jgtdiynm> In-Reply-To: <002401c4cdc7$94613100$80457ad5@jgtdiynm> X-Scanned-By: MIMEDefang 2.36 X-SPF-Result: relay.thorcom.net: 63.171.43.8 is neither permitted nor denied by domain of genesiswireless.us X-Spam-Score: 0.5 (/) X-Spam-Report: autolearn=no,HTML_MESSAGE=0.001,HTML_TITLE_EMPTY=0.544 Subject: Re: LF: Loading Coils 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_MESSAGE,HTML_TITLE_EMPTY 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 I was working on a Cisco router yesterday and found a bad surface mount ferrite. I asked the other guy in my department if he could look on a parts board for a ferrite bead and he returned later to say there isn't any on the other boards. I said hmmm, let me look. Sure enough it wasn't labeled FB whatever but Z1 or something and I had to explain to him that in radio talk that Z means impedance and ferrite beads are a resistance to RF hence the Z labeling. I guess us amateur radio operators have an edge against the new people coming out of college thinking they know lots about electronics. Oh well...

Mike

James Moritz wrote:

Dear Andy, LF Group,

----- Original Message -----
From: Andy <>
To: <rsgb_lf_group@blacksheep.org>
Sent: Wednesday, November 17, 2004 2:46 PM
Subject: RE: LF: Loading Coils

I share my office with some young electronics engineers and was
surprised that they know very little about RF inductors or Q factor.
It must be a dying art !

Its not just young electronics engineers who know nothing about inductors.

work with a number of middle aged ones (well, 30 - 50 anyway) who also

know

next to nothing about inductors, wire antennas, or even radio

communications.

Actually, there is quite a lot of interest in academic and engineering
circles about inductor Q at the moment - but this is about inductors on
ICs - little planar spirals of several nH that occupy quite a lot of space
on most "system on a chip" ICs containing RF transceivers for "Bluetooth",
"WiFi" and so on. A state-of-the-art Q for one of these is about 5 - 10 ...
even with lousy Q like this, circuit designers find they can't live without
them for amplifiers and oscillators and the like, despite spending half a
century inventing circuits to try and get rid of inductors!

some graduates can't even apply ohms law to a practical
situation.


As someone who occasionally has to help undergraduates do this, I'm afraid I
have to agree. V = I x R they can usually cope with, but I = V/R is a bit
more challenging, involving division as it does ... any mention of kilohms,
microamps etc. and all bets are off!

Cheers, Jim Moritz
73 de M0BMU