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 x1OINukf018150 for ; Sun, 24 Feb 2019 19:24:02 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1gxyO2-0007pf-Uz for rs_out_1@blacksheep.org; Sun, 24 Feb 2019 18:20:26 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1gxyO2-0007pW-Dn for rsgb_lf_group@blacksheep.org; Sun, 24 Feb 2019 18:20:26 +0000 Received: from mail-vk1-xa2f.google.com ([2607:f8b0:4864:20::a2f]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.91) (envelope-from ) id 1gxyO0-0003py-0Z for rsgb_lf_group@blacksheep.org; Sun, 24 Feb 2019 18:20:25 +0000 Received: by mail-vk1-xa2f.google.com with SMTP id j68so1601258vke.13 for ; Sun, 24 Feb 2019 10:20:23 -0800 (PST) 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=mime-version:references:in-reply-to:from:date:message-id:subject:to; bh=BX+CEjOLK5lM23G6u0SXuszZtE5exmNRjv41WxYpHA8=; b=fHwlXFaKTJp8sgjJrXKZPjFD1LohB4SusOI/utOdZr8nBN1TlQCVSGRVIrWsGZ1xN+ IyMt3ZeGdXe5OA+l03fl1c0obGh4tuHYk1go5O0Spbt6tNlEAoyMsXq3gEd3qtbzeShr 6UQe/Ue0uyLKQtFzvG7nS38QzEJLBW26Cs8ReF+v/yn8EqPSiBGF9CAO5GlVTywFG4LF dVoqAn2OSwKtcNg7KcSafaFS/mlRhTGf5VTBxqDWpCGYnpsji0xaNrTvlejL227PTumi 8t552SqHt2D/iNtcWHqIqRJvNilxB6oxIbSAoXMcEerg+pUO9dcrZarTfBRFqgOTrW7q lgqw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to; bh=BX+CEjOLK5lM23G6u0SXuszZtE5exmNRjv41WxYpHA8=; b=qNn/OxBHvrqvuFE0w+QZJPjolzPINGRTCcVuq9rznb8yWWksxZBAmsAZQ2RP6Udi2y MTwzocBJaJx7HBg71JquZwE9vnKPIpCtfZbfm5s9s0at99HYJo0PrrV+fVNPXldR3zan VhePsPPR9wu3aRLkiY+eM2nCTeUOE9gAQrDp7fvzQI+RuJ68CcW1euFRfug+tkBmh817 84qkOzIWVLaTl3kZupn0DDLvVoR4MdL/CN6GU0uUT1E0WS9mz1jwDDyrCrh73t6qoPsr I98w2VOjJoEUhty3mgwt1dfLPFIzsVoFlLFGROQDgvPFwbVO2GNiAmLWAB2nHSIYpP8n nXhw== X-Gm-Message-State: AHQUAubC7kwEOiVoaHwghwdTCEs8Wtlk1M4m2Qje3ugKnlqGI61PsoUu 5fmb/JvtuxBzaDGVNKPOtdc1swA/d6V1PGLv7T1aWNP0 X-Google-Smtp-Source: AHgI3IYIVlKxOzRenqNrI3Ohnx/LvGO18d35lnSGAL9fnvHTcdfYfjA0f0ZSrwlOokkxC96jEV6tW8SN/Hdk0vnwGag= X-Received: by 2002:a1f:91c4:: with SMTP id t187mr7429752vkd.86.1551032422312; Sun, 24 Feb 2019 10:20:22 -0800 (PST) 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> In-Reply-To: <81de6f2c-30cf-5142-fbd8-bd67416e97d7@no3m.net> From: Andy Talbot Date: Sun, 24 Feb 2019 18:20:02 +0000 Message-ID: To: "rsgb_lf_group@blacksheep.org" X-Spam-Score: 0.0 (/) 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: IN that case some sort of protection needs to be incorporated - and few have come up with really properly designed and foolproof circuitry. I use the technique adopted in the hold Decca transmitters, [...] Content analysis details: (0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [2607:f8b0:4864:20:0:0:0:a2f 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 (andy.g4jnt[at]gmail.com) 0.0 HTML_MESSAGE BODY: HTML included in message X-Scan-Signature: 081739af09bdcbecda01e4d970c01b31 Subject: Re: LF: Re: Class D current spikes Content-Type: multipart/alternative; boundary="0000000000009131960582a7e009" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_20_30,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 --0000000000009131960582a7e009 Content-Type: text/plain; charset="UTF-8" IN that case some sort of protection needs to be incorporated - and few have come up with really properly designed and foolproof circuitry. I use the technique adopted in the hold Decca transmitters, detailed here http://g4jnt.com/137tx.pdf but it assumes a tank circuit is in use. For transformer and traditional PI/Tee LPF arrangements it's not applicable I don't know of anyone who has used this technique outside designs based around that article that I've been told about- which seems amazing considering how absolutely robust and foolproof it is. Complete overload protection against any mismatch. I've seen all sorts of overload protection circuitry in use, current monitors and trips, Hall sensors etc etc But if there is going to be a current spike then it has to be designed-out in the first place. Choke fed PAs could perhaps have a bigger choke that can absorb a few 100us . Put voltage clamps in if overvoltage is the problem. Just Schottky diodes up and down to the rails. Andy www.g4jnt.com On Sun, 24 Feb 2019 at 18:08, Eric NO3M wrote: > Andy > > This recommendation is all well and good, but seems applicable 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. The spikes > would still be present and problematic. > > Other than Rik's suggestion of killing the lingering active high driver > output, it 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 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 should be using supply > line control. Switching the drive then trying to reduce rise /fall times > for keyclick elimination by controlling drive amplitude(something that > seems to be done in some designs) is really asking for trouble. Even > hard-switching drive gives its problems , as we see here repeatedly > > Instead, why not a simple emitter follower in the positive supply, then > you can apply waveform shaping to the base drive at low current, where > you've got full control. Even a 20A supply could be controlled this way > with a suitably rated transistor. Quite likely have to be a Darlington. > There will be a slight fixed drop across it, say 1V at saturation / full > power, so a few watts of dissipation, but it's only operating non saturated > for a short period during the rise / fall times. > > A power FET could be used, but you'd need a drive voltage Vgs higher than > the supply, albeit only a few mA capability; nothing a small switcher > module couldn't manage. > > Andy > www.g4jnt.com > > > > > --0000000000009131960582a7e009 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
IN that case some sort of prote= ction needs to be incorporated - and few have come up with really properly = designed and foolproof circuitry.
I use the technique adop= ted in the hold Decca transmitters, detailed here=C2=A0http://g4jnt.com/137tx.pdf=C2=A0 but it assumes a ta= nk circuit is in use.=C2=A0 =C2=A0 For transformer and traditional PI/Tee L= PF arrangements it's not applicable

= I don't know of anyone who has used this technique outside designs base= d around that article that I've been told about- which seems amazing co= nsidering how absolutely robust and foolproof it is.=C2=A0 =C2=A0Complete o= verload protection against any mismatch.=C2=A0 =C2=A0

I've seen all sorts of overload protection circuitry in u= se, current monitors and trips, Hall sensors etc etc=C2=A0 But if there is = going to be a current spike then it has to be designed-out in the first pla= ce.=C2=A0 =C2=A0Choke fed PAs could perhaps have a bigger choke that can ab= sorb a few 100us .=C2=A0 =C2=A0Put voltage clamps in if overvoltage is the = problem.=C2=A0 Just Schottky diodes up and down to the rails.


On Sun, 24 Feb 2019 at 18:08, Eric NO3M <no3m@no3m.net> wrote:
=20 =20 =20
Andy

This recommendation is all well and good, but seems applicable 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.=C2=A0 The spikes would still be present and problematic.=

Other than Rik's suggestion of killing the lingering active high driver output, it 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.=C2=A0 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:
=20
For on-off keying of a switch mode PA you really should be using supply line control.=C2=A0 Switching the drive then trying to reduce rise /fall times for keyclick elimination by controlling drive amplitude(something that seems to be done in some designs) is really asking for trouble.=C2=A0 Even hard-switching drive gives its problems , as we see here repeatedly

Instead, why not a simple emitter follower in the positive supply, then you can apply waveform shaping=C2=A0 to the base drive at low current, where you've got full control.=C2=A0 =C2=A0Even a 20= A supply could be controlled this way with a suitably rated transistor.=C2=A0 Quite likely have to be a Darlington.=C2=A0 =C2= =A0There will be a slight fixed drop across it, say 1V at saturation / full power, so a few watts of dissipation, but it's only operating non saturated for a short period during the rise / fall times.

A power FET could be used, but you'd need a drive voltage Vgs higher than the supply, albeit only a few mA capability; nothing a small switcher module couldn't manage.
=C2=A0



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