Return-Path: Received: (qmail 12285 invoked from network); 20 Feb 2004 23:30:14 -0000 Received: from unknown (HELO ptb-mxscan02.plus.net) (212.159.14.236) by ptb-mailstore03.plus.net with SMTP; 20 Feb 2004 23:30:14 -0000 Received: (qmail 18351 invoked from network); 20 Feb 2004 23:30:14 -0000 X-Filtered-by: Plusnet (hmail v1.01) X-Spam-detection-level: 11 X-Priority: 3 X-MSMail-Priority: Normal Received: from ptb-mxcore02.plus.net (212.159.14.216) by ptb-mxscan02.plus.net with SMTP; 20 Feb 2004 23:30:13 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore02.plus.net with esmtp (Exim) id 1AuK60-0004eb-TG for dave@picks.force9.co.uk; Fri, 20 Feb 2004 23:30:12 +0000 X-Fake-Domain: majordom Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1AuK5M-0001Au-RQ for rs_out@blacksheep.org; Fri, 20 Feb 2004 23:29:32 +0000 Received: from [165.212.11.110] (helo=cmsrelay01.mx.net) by post.thorcom.com with smtp (Exim 4.14) id 1AuK5F-0001A0-AG for rsgb_lf_group@blacksheep.org; Fri, 20 Feb 2004 23:29:25 +0000 Received: from uadvg130.cms.usa.net (165.212.11.130) by cmsoutbound.mx.net with SMTP; 20 Feb 2004 23:28:53 -0000 Received: from usa.net [151.41.157.95] by uadvg130.cms.usa.net (ASMTP/dibene@usa.net) via mtad (C8.MAIN.3.13N) with ESMTP id 212iBTXCz0050M30; Fri, 20 Feb 2004 23:28:51 GMT X-USANET-Auth: 151.41.157.95 AUTH dibene@usa.net usa.net Message-ID: <4036984A.8060808@usa.net> Date: Fri, 20 Feb 2004 23:29:14 +0000 From: "Alberto di Bene" User-Agent: Mozilla/5.0 (Windows; U; Win98; en-US; rv:1.4) Gecko/20030624 Netscape/7.1 (ax) X-Accept-Language: en-us, en MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: In-reply-to: Subject: LF: RF Current meter Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Checker-Version: SpamAssassin 2.60 (1.212-2003-09-23-exp) on post.thorcom.com X-Spam-Level: ** X-Spam-Status: No, hits=2.8 required=5.0 tests=FAKE_HELO_USA_NET autolearn=no version=2.60 X-SA-Exim-Scanned: Yes Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-PN-SPAMFiltered: yes X-Spam-Rating: 1 Wouldn't that mean that you measured the current in a point where the impedance was about 2250 ohm ? (Supposing the 100W were RF power, if the PA efficiency is less than 100% that impedance is lower). 5 W into 50 ohm -> 0.316 A -> full scale 0.316/0.75 = 0.422 A 50% of that current = 0.211 A R = W/I^2 = 100/0.211^2 = 2250 ohm 73 Alberto I2PHD ------------------------------- G4WGT - Gary wrote: >An interesting occurrence when testing the simple RF clip on current meter >on the bench, I used my Marathon 5w Tx to provide RF to test the meter, >separated a small section of the coax inner & shield, fed into 50R dummy >load & got 75% fsd, so I shunted the meter until it just moved off the >bottom of the scale, went to the base of the LF vertical whilst transmitting >with about 100w DC i/p but there was no reading on the meter, I then removed >the shunt & did the same test & got about a 50% fsd reading, I can't work >that one out. >