Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-1.8 required=5.0 tests=FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,HTML_MESSAGE,RCVD_IN_DNSWL_MED, RCVD_IN_SORBS_SPAM,SPF_PASS,T_DKIM_INVALID autolearn=ham autolearn_force=no version=3.4.0 X-Spam-DCC: EATSERVER: mailn 1166; 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 v3SDb70r022550 for ; Fri, 28 Apr 2017 15:37:08 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1d4616-0007KJ-Cb for rs_out_1@blacksheep.org; Fri, 28 Apr 2017 14:33:00 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1d4614-0007K8-H2 for rsgb_lf_group@blacksheep.org; Fri, 28 Apr 2017 14:32:58 +0100 Received: from omr-a011e.mx.aol.com ([204.29.186.59]) by relay1.thorcom.net with esmtps (TLSv1:DHE-RSA-AES256-SHA:256) (Exim 4.89) (envelope-from ) id 1d460z-00053E-1T for rsgb_lf_group@blacksheep.org; Fri, 28 Apr 2017 14:32:57 +0100 Received: from mtaomg-aal02.mx.aol.com (mtaomg-aal02.mx.aol.com [172.27.20.208]) by omr-a011e.mx.aol.com (Outbound Mail Relay) with ESMTP id A756738000B1 for ; Fri, 28 Apr 2017 09:32:50 -0400 (EDT) Received: from core-acb01f.mail.aol.com (core-acb01.mail.aol.com [172.27.24.1]) by mtaomg-aal02.mx.aol.com (OMAG/Core Interface) with ESMTP id 3D54438000081 for ; Fri, 28 Apr 2017 09:32:50 -0400 (EDT) Received: from 188.192.95.60 by webprd-m107.mail.aol.com (10.74.63.49) with HTTP (WebMailUI); Fri, 28 Apr 2017 09:32:49 -0400 Date: Fri, 28 Apr 2017 09:32:50 -0400 From: Markus Vester To: rsgb_lf_group@blacksheep.org Message-Id: <15bb4c39bb3-2379-b39e@webprd-m107.mail.aol.com> In-Reply-To: <1907129228.20170428123626@gmail.com> MIME-Version: 1.0 X-MB-Message-Source: WebUI X-MB-Message-Type: User X-Mailer: JAS STD X-Originating-IP: [188.192.95.60] x-aol-global-disposition: G DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mx.aol.com; s=20150623; t=1493386370; bh=Vl99mPZuSypsskKr7FURnenVQjkB3NYjY/z+ER+LzQg=; h=From:To:Subject:Message-Id:Date:MIME-Version:Content-Type; b=I3WLwlq1OAmSteEZAFUc9CtAUG2Q7tJOt4iSxxEXGAC6Lqp4XH3wiPaztnwkCNnMr d5XZSOOlFHX+UTJ9KY0AxgaZWRI3a+Vta2GoEUuyzIUOtRToshPxXAtVyH9uQvxsaE kQtxiiUbpkwmN1HqEsl4RfBuXbPYKiQzaoZmp0DA= x-aol-sid: 3039ac1b14d0590344827c12 X-Scan-Signature: 47a967f57bae6380aac0a0062beb1b4e Subject: Re: LF: Varistor spike management Content-Type: multipart/alternative; boundary="----=_Part_57747_973716336.1493386369969" 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: 11503 ------=_Part_57747_973716336.1493386369969 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Hi Chris, the "overshoot" screenshot seems to indicate that ihe peak is not only a sh= ort RF spike but caused by a longer positive excursion of the supply voltag= e. This is probably caused by the suddenly ending current consumption when = the carrier goes off. If the supply line contains significant inductance, i= t will try to sustain the current and thus increase the voltage. In a switc= hmode supply this could easily happen in the output ripple filter. A larger= electrolytic cap (e.g. 100 uF) across the DC line near the PA should fix i= t. =20 Best 73, Markus (DF6NM) -----Urspr=C3=BCngliche Mitteilung-----=20 Von: Chris Wilson An: DK7FC Verschickt: Fr, 28. Apr 2017 13:38 Betreff: Re: LF: Varistor spike management 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=20 > the spikes. Anyway i put a 150 Ohm / 220 pF (for LF) series RC paralell > to the Drain-Source... > 73, Stefan --=20 Best regards, Chris mailto:dead_fets@gmail.com ------=_Part_57747_973716336.1493386369969 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable
Hi Chris,

the "overshoot" screenshot seems t= o indicate that ihe peak is not only a short RF spike but ca= used by a longer positive excursion of the supply voltage. This i= s probably caused by the suddenly ending current consumption when the&= nbsp;carrier goes off. If the supply line contains significant inducta= nce, it will try to sustain the current and thus increase the vol= tage. In a switchmode supply this could easily happen in the = ;output ripple filter. A larger electrolytic cap (e.g. 100 uF) across the D= C line near the PA should fix it.   

Best 73,Markus (DF6NM)

-----Urspr=C3=BCngliche Mitteilung-----
Von: Chr= is Wilson <dead.fets@gmail.com>
An: DK7FC <rsgb_lf_group@blacks= heep.org>
Verschickt: Fr, 28. Apr 2017 13:38
Betreff: Re: LF: Vari= stor spike management

28th May 2017

Hi Stefan, remarkab= le 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 re= aches

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 par= t time LF grabber is at http://www.chriswilson.tv/grabber.html


>= ; Hi Chris,

> Which type of FETs are you using?
> The IRFP4= 60A for example has a built in Z-diode which seems to handle
> the s= pikes. Anyway i put a 150 Ohm / 220 pF (for LF) series RC paralell
> = to the Drain-Source...

> 73, Stefan


--
Best regard= s,
Chris mailto:dead_fets@gmail.com


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