Return-Path: Received: (qmail 10939 invoked from network); 15 Nov 2002 12:42:14 -0000 Received: from murphys.services.quay.plus.net (212.159.14.225) by mailstore with SMTP; 15 Nov 2002 12:42:14 -0000 Received: (qmail 19769 invoked from network); 15 Nov 2002 11:41:23 -0000 Received: from post.thorcom.com (193.82.116.70) by murphys.services.quay.plus.net with SMTP; 15 Nov 2002 11:41:23 -0000 X-SQ: A Received: from majordom by post.thorcom.com with local (Exim 4.10) id 18Cepp-0005pI-00 for rsgb_lf_group-outgoing@blacksheep.org; Fri, 15 Nov 2002 11:40:29 +0000 Received: from [165.254.158.18] (helo=mail.mcf.com) by post.thorcom.com with esmtp (Exim 4.10) id 18Cepp-0005p9-00 for rsgb_lf_group@blacksheep.org; Fri, 15 Nov 2002 11:40:29 +0000 Received: from parissn2 (213.41.137.138) by mail.mcf.com with ESMTP (Eudora Internet Mail Server 3.2a6) for ; Fri, 15 Nov 2002 06:40:29 -0500 Message-ID: <001501c28c9b$eda10ed0$0700000a@parissn2> From: "Stewart Nelson" To: rsgb_lf_group@blacksheep.org References: <3DD35969.30941.58250D@localhost> <004801c28bb7$b2c00580$015e89d9@jackie> <5.1.0.14.0.20021114135046.02a5e660@pb623250.kuleuven.be> <000b01c28c92$7ca50aa0$0504210a@c.scope> Date: Fri, 15 Nov 2002 12:41:23 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2720.3000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Subject: LF: Re: Calibrating LF Current Meters Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Status: No, hits=-0.3 required=5.0tests=QUOTED_EMAIL_TEXT,REFERENCES,SPAM_PHRASE_00_01, USER_AGENT_OEversion=2.42 Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Hi Hugh, You don't say what other instruments you have available, but here are a few suggestions: 1. Measure the RF voltage across the dummy load with a scope. Determine current by knowing or measuring its resistance. A dummy load usable at 10 meters should be very close to its DC resistance at 1.8 MHz. 2. Measure how hot the dummy load gets, then see how much DC or mains frequency current it takes to produce the same final temperature. 3. Put a suitable light bulb in series. Measure the brightness with a light meter, then see how much DC or mains frequency current it takes to produce the same brightness. 4. Rig a simple diode rectifier to measure the RF voltage. Either compensate the reading with an estimate of the diode drop, or calibrate the rectifier at mains frequency. 73, Stewart KK7KA ----- Original Message ----- From: "g6tmk" To: Sent: Friday, November 15, 2002 11:33 AM Subject: LF: Calibrating LF Current Meters > Hi All, > I built the little antenna current meter shown in the LF Experimenters > Handbook last night (Page 81). > And it works. I measured the current from my HF rig into a dummy load at > 1.8MHz, and it gave sensible results ... > But how can I calibrate it - how do I know that an indicated Amp really is > an Amp. > My DVMs, being intended for mains current measurement, don't have the > frequency response. > How have other people done it ? Any ideas ? > 73 > Hugh M0WYE