Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=0.0 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, SPF_PASS,T_DKIM_INVALID,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 X-Spam-DCC: EATSERVER: mailn 1166; Body=3 Fuz1=3 Fuz2=3 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by lipkowski.org (8.14.4/8.14.4/Debian-8+deb8u2) with ESMTP id v75Bm5ei012733 for ; Sat, 5 Aug 2017 13:48:06 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1ddxUf-0002j0-6I for rs_out_1@blacksheep.org; Sat, 05 Aug 2017 12:43:45 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1ddxUY-0002ir-VR for rsgb_lf_group@blacksheep.org; Sat, 05 Aug 2017 12:43:38 +0100 Received: from rgout0804.bt.lon5.cpcloud.co.uk ([65.20.0.151]) by relay1.thorcom.net with esmtp (Exim 4.89) (envelope-from ) id 1ddxUW-0007uG-0G for rsgb_lf_group@blacksheep.org; Sat, 05 Aug 2017 12:43:37 +0100 X-OWM-Source-IP: 86.185.176.70 (GB) X-OWM-Env-Sender: alan.melia@btinternet.com X-Junkmail-Premium-Raw: score=12/50,refid=2.7.2:2017.8.5.112716:17:12.455,ip=,rules=__HAS_MSGID, __SANE_MSGID, MSGID_32HEX_LC, INVALID_MSGID_NO_FQDN, __MSGID_32HEX, __HAS_FROM, __FRAUD_WEBMAIL_FROM, __TO_MALFORMED_2, __TO_NO_NAME, __REFERENCES, __BOUNCE_CHALLENGE_SUBJ, __BOUNCE_NDR_SUBJ_EXEMPT, __SUBJ_ALPHA_END, __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_NO_WWW, __SUBJ_ALPHA_NEGATE, __FORWARDED_MSG, __NO_HTML_TAG_RAW, BODYTEXTP_SIZE_3000_LESS, BODY_SIZE_1600_1699, __MIME_TEXT_P1, __MIME_TEXT_ONLY, __URI_NS, HTML_00_01, HTML_00_10, BODY_SIZE_5000_LESS, __FRAUD_WEBMAIL, MSG_THREAD, LEGITIMATE_SIGNS, __OUTLOOK_MUA, __PHISH_SPEAR_STRUCTURE_1, BODY_SIZE_2000_LESS, __MIME_TEXT_P, FORGED_MUA_OUTLOOK, REFERENCES, NO_URI_HTTPS, BODY_SIZE_7000_LESS Received: from gnat (86.185.176.70) by rgout08.bt.lon5.cpcloud.co.uk (9.0.019.13-1) (authenticated as alan.melia@btinternet.com) id 58BFF0800FF9A88C for rsgb_lf_group@blacksheep.org; Sat, 5 Aug 2017 12:43:35 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=btinternet.com; s=btcpcloud; t=1501933416; bh=pJKg1+76ju4VHa+0QhY29I4XfDDo4+q+p+ryeq2wEt8=; h=Message-ID:From:To:References:Subject:Date:MIME-Version:X-Mailer; b=pWcSaUOAvsz3ZkUBzZD95UVf/nnUjRhI9o9ME05JCLpdXcZmEiGgQk9tt78nB4VAw7dDDI/Tf6t6CBWde56KfoCAN3G5cVVENcgKy7MVYe4e0/kvHQh88PZPggO+WhyDxuEJjZ3/3tWM99v6xkLtBsu4ZlukbnqGgpO9W+uMmtY= Message-ID: <6EA1FC1ACFD44C549E12D4C74CEE1E79@gnat> From: "Alan Melia" To: References: <0883B95D3F4D417F975C59A900E1A838@gnat> <3D9A092BFA65418DBEE13188A4C58580@gnat> <92ce2c22-a887-bb8f-6bc2-6f03b51899d6@t-online.de> Date: Sat, 5 Aug 2017 12:34:53 +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: 046f068074e745d5c60ca47deee9b503 Subject: LF: Re: G4HUP aerial current meter/ hazards Content-Type: text/plain; format=flowed; charset="utf-8"; reply-type=response 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 2.75 Status: RO X-Status: X-Keywords: X-UID: 12336 Hi Wolf yes the problems of unknown cores noted. Thetypes supplied in the kits have been tested. We have not seen fracture but if you modify the circuit for higher power it is a point to bear in mind. There seem to be a wide range of core quality and parameters sold in this format. Motto "if it gets warm it is lossy" :-)) Thanks and Best Wishes Alan G3NYK ----- Original Message ----- From: "Dr. Wolf Ostwald" To: Sent: Saturday, August 05, 2017 6:38 AM Subject: LF: G4HUP aerial current meter/ hazards > good morning ! > a current transformer with ferrites of unknown origin and virtues is a > very risky thing. > As these cores are widely available on swapmeets its a lure to use them. > But they can be tested. I blew a few of them by just putting them on with > a single primary turn and with power less than a hundred watts they got > hot and broke. > The losses can be extremely high. > It does not help to measure their magnetic constant. As that has not much > to do with frequency dependent losses. > a way to find out is to use a 50 ohm load and measure the RF voltage > across the terminals. Then u just put the toroid over the "hot" side of > the resistor terminals. > If the measured RF voltage drops heavily, the core is useless. You dont > want it to block, u want to derive some RF for measuring purposes. > The above core would go into pieces and additionally as it poses a high > inductance to ur feedline, the amplifier stage may go south, depending on > the safety factor involved with ur construction . > > 73 de wolf df2py >