Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=5.0 tests=FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_MED,SPF_PASS, T_DKIM_INVALID autolearn=ham autolearn_force=no version=3.4.0 X-Spam-DCC: INFN-TO: mailn 1233; Body=2 Fuz1=2 Fuz2=2 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by lipkowski.org (8.14.4/8.14.4/Debian-8+deb8u1) with ESMTP id v3SBfr2H021686 for ; Fri, 28 Apr 2017 13:41:55 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1d44CO-0006Uk-Rw for rs_out_1@blacksheep.org; Fri, 28 Apr 2017 12:36:32 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1d44CO-0006Ub-Gi for rsgb_lf_group@blacksheep.org; Fri, 28 Apr 2017 12:36:32 +0100 Received: from mail-wm0-x235.google.com ([2a00:1450:400c:c09::235]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1d44CL-0004hG-0H for rsgb_lf_group@blacksheep.org; Fri, 28 Apr 2017 12:36:31 +0100 Received: by mail-wm0-x235.google.com with SMTP id w64so39834024wma.0 for ; Fri, 28 Apr 2017 04:36:28 -0700 (PDT) X-DKIM-Result: Domain=gmail.com Result=Good and Known Domain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:date:message-id:to:subject:in-reply-to:references:mime-version :content-transfer-encoding; bh=nDvja1B5Dmx4KpDNn7OAoOIlMTdpx2fGxq1NlYXPl+8=; b=htD4zRbr2AKj4d+Dv6vqhV+lq+Cu7s/b0Le9DX/BMSgJO9G528r8i/uv3qFCH7gG81 Nsd5Cis2iUFmQbw1nSS+MRKz5uLsYWVTQggf4UeYdzU37QU9SE+z/S8H2u6gj7AlmlOs 2kCG+0G3WU4EyUqY3k/snlfXoxLDJKK4rl83FNyC6FmXv0U8RsdDkuW/uQhkmnWy18/Q ut1h8tZ6/mADIgnUANjJ9qMqNlQ1ayBCxR53VBz73Yrs+YTqRhnzuNAnqNOD7tfTjc62 sxOkJJQaObjotJE5sE+Z7cyg4YxVf34iztfY5ATGMceQ/i2stvbRq9mJE6NIHExg5Sf+ Xhvw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:date:message-id:to:subject:in-reply-to :references:mime-version:content-transfer-encoding; bh=nDvja1B5Dmx4KpDNn7OAoOIlMTdpx2fGxq1NlYXPl+8=; b=gbPl0qYTwuuuMSPrcI/bZ5ZZRXqIvAeItxkZNcYmYK0GvuHvvoyWJjFaeFbQpZjgAr CZpDV3Tf6W2fPn2wJ+9BfIFv1DqjVdRzwf6Sgk+Vcql7bV6x4rPrZIqdSyRGHPV+zcZl dmhBBbIeF8RFjQP3WTZEXnWLaxpOIvu/poVFLcWYtHPCzhbin1A2iYcJPVgr/RMIsotv 4DSJYNZ2ZaBTZ0oAYQkKRXd9U8MePkBIqon+vQuR4SBN2XIY1R/l69abCYO8dh8vBkFn fluLV4lxnMj3m02zIRdcSs9K/yXMT7LP2lSwHJlh6EFFQ1uEnsXCzx0eV8wNzVI4pS+I HpYQ== X-Gm-Message-State: AN3rC/4wUf6KKj5qdfrHhMlQ40ZBwK0Zd2HVq4SNWmwT1H2ZAGYvoCsq 0WdML6pdfXxjl/oE X-Received: by 10.28.87.70 with SMTP id l67mr5010502wmb.37.1493379388119; Fri, 28 Apr 2017 04:36:28 -0700 (PDT) Received: from OfficeWin7.lan (82-70-254-222.dsl.in-addr.zen.co.uk. [82.70.254.222]) by smtp.gmail.com with ESMTPSA id p17sm5788142wmd.11.2017.04.28.04.36.27 for (version=TLS1 cipher=AES128-SHA bits=128/128); Fri, 28 Apr 2017 04:36:27 -0700 (PDT) From: Chris Wilson X-Google-Original-From: Chris Wilson Date: Fri, 28 Apr 2017 12:36:26 +0100 X-Priority: 3 (Normal) Message-ID: <1907129228.20170428123626@gmail.com> To: DK7FC In-Reply-To: <5901FD30.5010902@posteo.de> References: <1106627522.20170427150315@gmail.com> <5901FD30.5010902@posteo.de> MIME-Version: 1.0 X-Scan-Signature: a6b6ffaf48fdddf1ed5c25dc4bf03ee1 Subject: Re: LF: Varistor spike management Content-Type: text/plain; charset=us-ascii 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: 11500 28th May 2017 Hi Stefan, remarkable work on VLF, congratulations!! I see these with all FET's but I acquired very cheaply some Wolfspeed FETs with a lot of overhead. These spikes sometimes kill lesser ones. If you follow these links you can see the normal gate and drain waveforms, and the drain waveform without a Varistor as an OPERA TX period ends, i took the latter from a series of screenshots showing the highest level the close TX spike reaches http://www.gatesgarth.com/wolfspeed-scope-capture-50v.jpg http://www.gatesgarth.com/wolfspeed-overshoot-50v.jpg http://www.gatesgarth.com/wolfspeed.pdf Best regards, Chris 2E0ILY mailto:chris@gatesgarth.com My part time LF grabber is at http://www.chriswilson.tv/grabber.html > Hi Chris, > Which type of FETs are you using? > The IRFP460A for example has a built in Z-diode which seems to handle > the spikes. Anyway i put a 150 Ohm / 220 pF (for LF) series RC paralell > to the Drain-Source... > 73, Stefan -- Best regards, Chris mailto:dead_fets@gmail.com