Return-Path: Received: from rly-md04.mx.aol.com (rly-md04.mail.aol.com [172.20.29.142]) by air-md10.mail.aol.com (v125.7) with ESMTP id MAILINMD102-8ff4adb2d8e23; Sun, 18 Oct 2009 11:00:49 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-md04.mx.aol.com (v125.7) with ESMTP id MAILRELAYINMD047-8ff4adb2d8e23; Sun, 18 Oct 2009 11:00:32 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1MzXEj-0003By-Vq for rs_out_1@blacksheep.org; Sun, 18 Oct 2009 15:59:57 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1MzXEj-0003Bp-A4 for rsgb_lf_group@blacksheep.org; Sun, 18 Oct 2009 15:59:57 +0100 Received: from qmta08.westchester.pa.mail.comcast.net ([76.96.62.80]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1MzXD9-0003nt-KC for rsgb_lf_group@blacksheep.org; Sun, 18 Oct 2009 15:58:20 +0100 Received: from OMTA10.westchester.pa.mail.comcast.net ([76.96.62.28]) by QMTA08.westchester.pa.mail.comcast.net with comcast id uEd11c0030cZkys58EyoLc; Sun, 18 Oct 2009 14:58:48 +0000 Received: from JAYDELL ([65.96.107.144]) by OMTA10.westchester.pa.mail.comcast.net with comcast id uEzd1c00336xPMd3WEzds9; Sun, 18 Oct 2009 14:59:37 +0000 Message-ID: <002701ca5003$9c046c60$8d01a8c0@JAYDELL> From: To: References: <007201ca4ff9$cce15190$0301a8c0@mal769a60aa920> <8FD1DC2A56674846A459F7CD0ADB7468@IBM7FFA209F07C> Date: Sun, 18 Oct 2009 10:59:36 -0400 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-Karma: unknown: X-Spam-Score: 0.6 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001,NO_REAL_NAME=0.55 Subject: LF: Re: Re: Re: AF Amps at 136 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0023_01CA4FE2.14C57AD0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: * X-Spam-Status: No, hits=1.1 required=5.0 tests=HTML_30_40,HTML_MESSAGE, NO_REAL_NAME 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 X-AOL-IP: 193.82.116.20 ------=_NextPart_000_0023_01CA4FE2.14C57AD0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 8bit Chris See links below...audio amps used on LF, MF. These Hafler amps were selected because they are rated to 300 kHz right out of the box. Probably won't find similar performance in very many amps. I only use the Haflers for modes requiring linear amplification - otherwise I run a class D setup. http://www.w1vd.com/page21.html http://www.w1vd.com/page23.html http://www.w1vd.com/9505MF.html Jay W1VD WD2XNS WE2XGR/2 ----- Original Message ----- From: Chris To: rsgb_lf_group@blacksheep.org Sent: Sunday, October 18, 2009 10:11 AM Subject: LF: Re: Re: AF Amps at 136 Thanks for your comments Mal, I did wonder if such an approach was wise. Let's see what others have to say on the matter. I also have my suspicions about FETs in class D and the level of crud that could result. Thanks again. Chris, G4AYT. ----- Original Message ----- From: mal hamilton To: rsgb_lf_group@blacksheep.org Sent: Sunday, October 18, 2009 2:49 PM Subject: LF: Re: AF Amps at 136 Chris Do not use audio amps for RF. Build a class D or E amp and operate trouble free. Audio amps were tried by some in the early days but never worked properly. Read the horror stories of yesteryears about using audio amps for RF applications. Buckets of burnt out FETS. 73 De Mal/g3kev ----- Original Message ----- From: Chris To: RSGB LF Group Sent: Sunday, October 18, 2009 2:13 PM Subject: LF: AF Amps at 136 Hi All, Just started constructing TX for 136kHz, noticed Maplin do a Velleman audio PA kit that is rated at 200W (100W RMS into 4R). OK there's no mains transformer or heat sink, but reckon it's good value at £14.99. Point is the specs also say the minus 3db frequency response is 3Hz / 200kHz. The RSGB books 'LF Today' refer to using audio amps as PAs at 136 with 'a few modifications'. Does anybody know where these modifications are documented? I guess there's nothing major, reduce a few cap values? Remove Zobel Network etc.?? If anyone has experience with this approach I would appreciate some hints. Thanks. Chris, G4AYT, Whitstable. -------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.422 / Virus Database: 270.14.20/2443 - Release Date: 10/17/09 13:08:00 ------=_NextPart_000_0023_01CA4FE2.14C57AD0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Chris
 
See links below...audio=20 amps used on LF, MF. These Hafler amps were select= ed because=20 they are rated to 300 kHz right out of the box. Probably won't fi= nd similar=20 performance in very many amps. I only use the Haflers for modes= requiring=20 linear amplification - otherwise I run a class D=20 setup.  
 
 
 
 
Jay W1VD  WD2XNS  WE2XGR/2<= /FONT>
----- Original Message -----
From:=20 Chris
Sent: Sunday, October 18, 200= 9 10:11=20 AM
Subject: LF: Re: Re: AF Amps= at 136

Thanks for your comments Mal, I did= wonder if=20 such an approach was wise. Let's see what others have to say on the= matter. I=20 also have my suspicions about FETs in class D and the level of crud= that=20 could result.
Thanks again.
Chris, G4AYT.
----- Original Message -----
From:=20 mal=20 hamilton
Sent: Sunday, October 18,= 2009 2:49=20 PM
Subject: LF: Re: AF Amps at= 136

Chris
Do  not use audio amps for= RF. Build a=20 class D or E amp and operate trouble free. Audio amps were tried= by some in=20 the early days but never worked properly.
Read the horror stories of yester= years about=20 using audio amps for RF applications. Buckets of burnt out=20 FETS.
73 De Mal/g3kev
 
----- Original Message -----
From:=20 Chris
Sent: Sunday, October 18,= 2009 2:13=20 PM
Subject: LF: AF Amps at= 136

Hi All,
Just started constructing TX fo= r 136kHz,=20 noticed Maplin do a Velleman audio PA kit that is rated at 200W= (100W RMS=20 into 4R). OK there's no mains transformer or heat sink, but reck= on it's=20 good value at =A314.99. Point is the specs also say the minus=20 3db frequency response is 3Hz / 200kHz.
The RSGB books 'LF Today' refer= to using=20 audio amps as PAs at 136 with 'a few modifications'. Does anybod= y know=20 where these modifications are documented? I guess there's nothin= g major,=20 reduce a few cap values? Remove Zobel Network etc.?? If anyone= has=20 experience with this approach I would appreciate some hints.=20 Thanks.
Chris, G4AYT, Whitstable.


No virus found in this incoming message.
Checked= by AVG -=20 www.avg.com
Version: 8.5.422 / Virus Database: 270.14.20/244= 3 -=20 Release Date: 10/17/09=20 13:08:00
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