Return-Path: X-Spam-DCC: paranoid 1170; Body=2 Fuz1=2 Fuz2=2 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, HTML_50_60,HTML_MESSAGE autolearn=no version=3.1.3 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by paranoid.lipkowski.org (8.13.7/8.13.7) with ESMTP id u08M4Hfi017992 for ; Fri, 8 Jan 2016 23:04:17 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1aHf5O-0003uq-9A for rs_out_1@blacksheep.org; Fri, 08 Jan 2016 22:00:42 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1aHf5N-0003uh-W9 for rsgb_lf_group@blacksheep.org; Fri, 08 Jan 2016 22:00:41 +0000 Received: from smtpout3.wanadoo.co.uk ([80.12.242.59] helo=smtpout.wanadoo.co.uk) by relay1.thorcom.net with esmtp (Exim 4.86) (envelope-from ) id 1aHf4K-0006Nz-5U for rsgb_lf_group@blacksheep.org; Fri, 08 Jan 2016 22:00:40 +0000 Received: from AGB ([95.150.80.237]) by mwinf5d35 with ME id 3ZzL1s00S57Cn6703ZzLnQ; Fri, 08 Jan 2016 22:59:20 +0100 X-ME-Helo: AGB X-ME-Date: Fri, 08 Jan 2016 22:59:20 +0100 X-ME-IP: 95.150.80.237 Message-ID: <4EA63FCADF204DB7B5E2936098C9A416@AGB> From: "Graham" To: References: In-Reply-To: Date: Fri, 8 Jan 2016 21:59:20 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 14.0.8117.416 X-MimeOLE: Produced By Microsoft MimeOLE V14.0.8117.416 X-Scan-Signature: 318d3d373f5ffaa82e0969bd1985b258 Subject: Re: LF: Linear Amp for LF Content-Type: multipart/alternative; boundary="----=_NextPart_000_0082_01D14A5F.D39682A0" 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 2.56 on 10.1.3.10 Status: RO X-Status: X-Keywords: X-UID: 6212 This is a multi-part message in MIME format. ------=_NextPart_000_0082_01D14A5F.D39682A0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable M0BMU from 2007 =20 http://w4dex.com/projects/EER_Transverter_v2.pdf G, From: Andy Talbot=20 Sent: Friday, January 08, 2016 9:45 PM To: rsgb_lf_group@blacksheep.org ; rsgb_lf_group@yahoogroups.co.uk=20 Subject: LF: Linear Amp for LF Are there any proven reliably designed LF amplifier designs power = amplifiers for 137 / 475? Wideband, covering both ideally Rated = for at least 300 Watts output, and ideally a lot more.=20 I saw G3YXM's low-HF design, and it looks promising for low frequency = use, but he appears to have not gone that way and went for a switchmode = version at LF/MF Of course, I could just redesign that, or something similar, using = suitable ferrite and a bit of feedback ,but it would be nice to avoid = reinventing too many wheels. Using switching MOSFETs as linear amps still doesn't feel quite right, = but enough people seem have managed it now (including my own design for = a low power one) that it looks a sound-enough route to follow up. The = one thing that does bother me about the technique is bias compensation = with temperature. It is really asking for active bias control, but in = a class-B or -AB design, where bias just affects standing current, that = gets more-than a bit tricky as a concept. Andy G4JNT ------=_NextPart_000_0082_01D14A5F.D39682A0 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable

M0BMU from 2007

http://w4dex.co= m/projects/EER_Transverter_v2.pdf

G,

From: Andy Talbot

Sent: Friday, January 08, 2016 9:45 PM

To: rsgb_lf_group@blacksheep.org= ; rsgb_lf_group@yahoogroups= .co.uk=20

Subject: LF: Linear Amp for LF

Are there any proven reliably designed LF amplifier = designs power=20 amplifiers for 137 / 475? Wideband, covering both = ideally=20 Rated for at least 300 Watts output, and ideally a lot = more.=20

I saw G3YXM's low-HF design, and it looks promising for low = frequency use,=20 but he appears to have not gone that way and went for a switchmode = version at=20 LF/MF

Of course, I could just redesign that, or something similar, using = suitable=20 ferrite and a bit of feedback ,but it would be nice to avoid reinventing = too=20 many wheels.

Using switching MOSFETs as linear amps still doesn't feel quite = right, but=20 enough people seem have managed it now (including my own design for a = low power=20 one) that it looks a sound-enough route to follow up. The = one thing=20 that does bother me about the technique is bias compensation with = temperature.=20 It is really asking for active bias control, but in a class-B or = -AB=20 design, where bias just affects standing current, that gets more-than a = bit=20 tricky as a concept.

Andy G4JNT

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