Return-Path: X-Spam-DCC: paranoid 1170; Body=2 Fuz1=2 Fuz2=2 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on lipkowski.org X-Spam-Level: * X-Spam-Status: No, score=1.7 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, FORGED_MUA_OUTLOOK autolearn=no version=3.1.3 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by paranoid.lipkowski.org (8.13.7/8.13.7) with ESMTP id t9KAgadZ031716 for ; Tue, 20 Oct 2015 12:42:36 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1ZoUJk-0003mQ-7d for rs_out_1@blacksheep.org; Tue, 20 Oct 2015 11:38:56 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1ZoUJj-0003mH-V6 for rsgb_lf_group@blacksheep.org; Tue, 20 Oct 2015 11:38:55 +0100 Received: from rgout0405.bt.lon5.cpcloud.co.uk ([65.20.0.218]) by relay1.thorcom.net with esmtp (Exim 4.86) (envelope-from ) id 1ZoUIi-0004xV-MF for rsgb_lf_group@blacksheep.org; Tue, 20 Oct 2015 11:38:54 +0100 X-OWM-Source-IP: 86.149.134.195 (GB) X-OWM-Env-Sender: alan.melia@btinternet.com X-CTCH-RefID: str=0001.0A090205.56261970.00F2,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0 X-Junkmail-Premium-Raw: score=38/50,refid=2.7.2:2015.10.14.111215:17:38.936,ip=86.149.134.195,rules=__HAS_MSGID, __SANE_MSGID, MSGID_32HEX_LC, INVALID_MSGID_NO_FQDN, __MSGID_32HEX, __HAS_FROM, __PHISH_FROM2, __FRAUD_WEBMAIL_FROM, __TO_MALFORMED_2, __TO_NO_NAME, __BOUNCE_CHALLENGE_SUBJ, __BOUNCE_NDR_SUBJ_EXEMPT, __MIME_VERSION, __CT, __CT_TEXT_PLAIN, __CTE, __HAS_X_PRIORITY, __HAS_MSMAIL_PRI, __HAS_X_MAILER, USER_AGENT_OE, __OUTLOOK_MUA_1, __USER_AGENT_MS_GENERIC, __ANY_URI, URI_ENDS_IN_HTML, __URI_NO_WWW, __CP_URI_IN_BODY, __SUBJ_ALPHA_NEGATE, __URI_IN_BODY, __FORWARDED_MSG, BODY_SIZE_1700_1799, BODYTEXTP_SIZE_3000_LESS, __MIME_TEXT_ONLY, RDNS_GENERIC_POOLED, __URI_NS, SXL_IP_DYNAMIC[195.134.149.86.fur], HTML_00_01, HTML_00_10, BODY_SIZE_5000_LESS, RDNS_SUSP_GENERIC, __PHISH_FROM, __OUTLOOK_MUA, __PHISH_SPEAR_STRUCTURE_1, BODY_SIZE_2000_LESS, RDNS_SUSP, __FRAUD_WEBMAIL, FORGED_MUA_OUTLOOK, BODY_SIZE_7000_LESS, __SINGLE_URI_TEXT, NO_URI_HTTPS, SINGLE_URI_IN_BODY X-CTCH-Spam: Unknown Received: from gnat (86.149.134.195) by rgout04.bt.lon5.cpcloud.co.uk (8.6.122.06) (authenticated as alan.melia@btinternet.com) id 561CE90400CDA5C4 for rsgb_lf_group@blacksheep.org; Tue, 20 Oct 2015 11:36:58 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=btinternet.com; s=btcpcloud; t=1445337434; bh=I2sbcAEs4TmpHVOQ1WMkLEBSvr6EkkwdUiRnKWb9EmI=; h=Message-ID:From:To:References:Subject:Date:MIME-Version:X-Mailer; b=tqN6a8nzPQuelK5ZDOWQ0qjY8HClExq5Ce+zGFD7OoYsbMdz7VxPOx4KBLAWXsMZjZmX/Pm8v5P8WTCk/mgJOtcHocemBwK3KEBrJchaQ8tAhPQZKTfrZQOw0fzPYnPAEO9vv+BIEER3lIYWrqCHp5IxA8/hxMnPAK+FnRbd17k= Message-ID: From: "Alan Melia" To: References: <1435044716.20151018182802@chriswilson.tv>, , <174420693.20151020102516@chriswilson.tv> <56262241.14467.4B37EB@mike.dennison.ntlworld.com> Date: Tue, 20 Oct 2015 11:37:34 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5931 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.6157 X-Scan-Signature: fc152e7304849b9a177649b85aea9f41 Subject: Re: Re[2]: LF: Where to measure antenna current? Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original Content-Transfer-Encoding: 7bit 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-Scanned-By: MIMEDefang 2.56 on 10.1.3.10 Status: O X-Status: X-Keywords: X-UID: 4547 Whilst as Mike says these ferrite RF-current meters are easy to make, a local friend of mine sells a kit which was originally intended for HF aerials but after a prod from couple of us was tested and works well at LF. See is web site at http://g4hup.com/index.html Dave G4HUP has devised a simple calibration that seems to work. I have to declare I get no pecunary advantage, though it might be good for a sticky bun next time we meet for coffee :-)) Alan G3NYK ----- Original Message ----- From: "Mike Dennison" To: Sent: Tuesday, October 20, 2015 11:15 AM Subject: Re: Re[2]: LF: Where to measure antenna current? >> Thanks John, yes it does help, much appreciated, but what I am still >> unsure of is if my Scopematch, that shows voltage and current >> waveforms, is also, on the current waveform, displaying antenna >> current? Does it not "do the same job" as a current meter? > > Your scope match measures the current in the feeder. This is not the > same as that in the antenna which may be a different impedance - > which is why you need a matching circuit (eg transformer). You can > measure the current at the (relatively) 'cold' end of the loading > coil where it meets the matching unit, so there's no need to deal > with the very high volts on the antenna wire itself. You can also > measure it in the earth lead, but I would not rely on earth current > whilst you still appear to have too much stray RF (see my earlier > posting). > > A current meter is easy to build. You don't even need to calbrate it > in the short term as you are unlikely to go anywhere near the legal > max ERP.. > > 73 de Mike, G3XDV >