Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by klubnl.pl (8.14.4/8.14.4/Debian-8+deb8u2) with ESMTP id x1OKiLjU018876 for ; Sun, 24 Feb 2019 21:44:22 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1gy0PQ-0008F4-Lr for rs_out_1@blacksheep.org; Sun, 24 Feb 2019 20:30:00 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1gy0MG-0008EY-JW for rsgb_lf_group@blacksheep.org; Sun, 24 Feb 2019 20:26:44 +0000 Received: from resqmta-ch2-10v.sys.comcast.net ([2001:558:fe21:29:69:252:207:42]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.91) (envelope-from ) id 1gy0MA-00043Y-35 for rsgb_lf_group@blacksheep.org; Sun, 24 Feb 2019 20:26:39 +0000 Received: from resomta-ch2-01v.sys.comcast.net ([69.252.207.97]) by resqmta-ch2-10v.sys.comcast.net with ESMTP id xxW2g9cWIEVJDy0M5gFe1m; Sun, 24 Feb 2019 20:26:33 +0000 X-DKIM-Result: Domain=comcast.net Result=Signature OK DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=comcast.net; s=q20161114; t=1551039993; bh=QAzXBhzH3PwRIrA7pQPuzzKjEuyRVaJOAFgQ19hyL4k=; h=Received:Received:From:Subject:To:Content-Type:MIME-Version:Date: Message-ID; b=BsA5dpn57WCe4J2gAGVnQO21rsJyFvOZw8lZvPM2Rq56YkK0zxEYncDohV6f036i9 9r6UicuTQeHIufHzzJPjfjuqBsnwjjkOZM6qKTSu1pdkpkUCfRhMzCJj1K2/E4kEvv GHA5Wv7NC4MI6WOYdbIXHfqbiVyTRe74vn1WDxx6fr3xmUf7bSVTyBjIJBXld3LT54 Z4pE8bG6s7zOsIPQ7qRk6sc+BFGJ0rW14HjTOAT9V70YOBiy5mh+gaxqc+2WUQPzyY VRxynuuv/cYc38Q1979UZeIgDThHhujX2Z7FQmdPY6VVZFiUtDxErkPN/+sgxr5Ok+ tPiHKTdYCDn7w== Received: from Optiplex980-PC ([73.4.253.141]) by resomta-ch2-01v.sys.comcast.net with ESMTPSA id y0M3gAUhhXnyHy0M4gGH0r; Sun, 24 Feb 2019 20:26:33 +0000 X-Xfinity-VAAS: gggruggvucftvghtrhhoucdtuddrgedutddrudeggddufeejucetufdoteggodetrfdotffvucfrrhhofhhilhgvmecuvehomhgtrghsthdqtfgvshhipdfqfgfvpdfpqffurfetoffkrfenuceurghilhhouhhtmecufedttdenucgonfftqdeuohhunhguqdftfedvucdlhedmnecujfgurhephffuvfgtgghffffkjggfsegrtderredtreejnecuhfhrohhmpedfjhhruhhsghhrohhvvgestghomhgtrghsthdrnhgvthdfuceojhhruhhsghhrohhvvgestghomhgtrghsthdrnhgvtheqnecuffhomhgrihhnpehggehjnhhtrdgtohhmnecukfhppeejfedrgedrvdehfedrudegudenucfrrghrrghmpehhvghlohepqfhpthhiphhlvgigleektddqrfevpdhinhgvthepjeefrdegrddvheefrddugedupdhmrghilhhfrhhomhepjhhruhhsghhrohhvvgestghomhgtrghsthdrnhgvthdprhgtphhtthhopehrshhgsggplhhfpghgrhhouhhpsegslhgrtghkshhhvggvphdrohhrghenucevlhhushhtvghrufhiiigvpedt X-Xfinity-VMeta: sc=5;st=legit From: "jrusgrove@comcast.net" To: "rsgb_lf_group@blacksheep.org" MIME-Version: 1.0 References: <043bec62-8144-5ff3-98a6-9f04699f6a4c@no3m.net> <1551011916482.41235@kuleuven.be> <1551014480338.17397@kuleuven.be> <27248150-3565-aeb8-9b66-53a9089fd4ab@n1bug.com> <1551018171015.45843@kuleuven.be> <81de6f2c-30cf-5142-fbd8-bd67416e97d7@no3m.net> Date: Sun, 24 Feb 2019 15:26:31 -0500 Message-ID: <1UTEDXzFHD.CcaJifW3lFj@optiplex980-pc> In-Reply-To: <81de6f2c-30cf-5142-fbd8-bd67416e97d7@no3m.net> User-Agent: OEClassic/2.9 (Win7.7601; P; 2018-07-03) X-Spam-Score: -0.7 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: Eric One or two FETs per phase? Jay W1VD Content analysis details: (-0.7 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.7 RCVD_IN_DNSWL_LOW RBL: Sender listed at http://www.dnswl.org/, low trust [2001:558:fe21:29:69:252:207:42 listed in] [list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (jrusgrove[at]comcast.net) 0.0 HTML_MESSAGE BODY: HTML included in message X-Scan-Signature: ad9c0e3658f56f4dbb01cd425a6a8031 Subject: Re: LF: Re: Class D current spikes Content-Type: multipart/alternative; boundary="EUHVcWIkh9sX0kiM=_tO6LDTMlqrnXJBRa" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.8 required=5.0 tests=HTML_30_40,HTML_MESSAGE, TO_ADDRESS_EQ_REAL autolearn=no version=2.63 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 This is a multi-part message in MIME format --EUHVcWIkh9sX0kiM=_tO6LDTMlqrnXJBRa Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Eric One or two FETs per phase? Jay W1VD ----- Original Message ----- From: Eric NO3M Reply-To: To: Sent: 2/24/2019 1:04:52 PM Subject: Re: LF: Re: Class D current spikes Andy This recommendation is all well and good, but seems applicable to only= CW where=20 either the operator is manually keying or using computer controlled ke= ying with=20 a constant carrier input. With digi modes (WSPR, JT9, etc.) that do not present a constant RF in= put, the=20 traditional PTT signaling is of no use as it keys active prior to the = RF=20 envelope start and goes inactive after the RF envelope ends. The spik= es would=20 still be present and problematic.=20 Other than=20 Rik's suggestion of killing the lingering active high driver output, i= t seems that only using a supply control scheme (whether driver or FET= drain supply) would require sampling the original RF input to detect = the end of the envelope and apply the key up (inactive) signal. Prior= to reaching the driver subsystem, the input RF would need to be delay= ed by some amount. 73 Eric NO3M On 2/24/19 9:41 AM, Andy Talbot wrote: For on-off keying of a switch mode PA you really should be using suppl= y line control. Switching the drive then trying to reduce rise /fall = times for keyclick elimination by controlling drive amplitude(somethin= g that seems to be done in some designs) is really asking for trouble.= Even hard-switching drive gives its problems , as we see here repeat= edly Instead, why not a simple emitter follower in the positive supply, the= n you can apply waveform shaping to the base drive at low current, wh= ere you've=20 got full control. Even a 20A supply could be controlled this way wit= h a=20 suitably rated transistor. Quite likely have to be a Darlington. Th= ere will=20 be a slight fixed drop across it, say 1V at saturation / full power, s= o a few=20 watts of dissipation, but=20 it's only operating non saturated for a short period during the rise /= fall times. A power FET could be used, but you'd=20 need a drive voltage Vgs higher than the supply, albeit only a few mA=20= capability; nothing a small switcher module couldn't manage. Andy=20 www.g4jnt.com --EUHVcWIkh9sX0kiM=_tO6LDTMlqrnXJBRa Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline
Eric
 
One or two FETs per phase?
 
Jay W1VD
 
 
----- Original Message -----
From: Eric NO3M <no3m@= no3m.net>
Sent: 2/24/2019 1:04:52 PM
Subject: Re: LF: Re: Class D current spikes
Andy

This recommendation is all well and good, but seems applic= able to only CW where either the operator is manually keying or using = computer controlled keying with a constant carrier input.

With = digi modes (WSPR, JT9, etc.) that do not present a constant RF input, = the traditional PTT signaling is of no use as it keys active prior to = the RF envelope start and goes inactive after the RF envelope ends.&nb= sp; The spikes would still be present and problematic.

Other t= han Rik's suggestion of killing the lingering active high driver outpu= t, it seems that only using a supply control scheme (whether driver or= FET drain supply) would require sampling the original RF input to det= ect the end of the envelope and apply the key up (inactive) signal.&nb= sp; Prior to reaching the driver subsystem, the input RF would need to= be delayed by some amount.

73 Eric NO3M


On 2/24/19 9:41 AM, Andy Talbot wrote:
For on-off keying of a switch mode PA you really shoul= d be using supply line control.  Switching the drive then trying = to reduce rise /fall times for keyclick elimination by controlling dri= ve amplitude(something that seems to be done in some designs) is reall= y asking for trouble.  Even hard-switching drive gives its proble= ms , as we see here repeatedly

Instead, why not a simple emitter follower in the posi= tive supply, then you can apply waveform shaping  to the base dri= ve at low current, where you've got full control.   Even a 2= 0A supply could be controlled this way with a suitably rated transisto= r.  Quite likely have to be a Darlington.   There will = be a slight fixed drop across it, say 1V at saturation / full power, s= o a few watts of dissipation, but it's only operating non saturated fo= r a short period during the rise / fall times.

A power FET could be used, but you'd need a drive volt= age Vgs higher than the supply, albeit only a few mA capability; nothi= ng a small switcher module couldn't manage.

 
Andy=20

<= /DIV>



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