Return-Path: Received: from rly-ma03.mx.aol.com (rly-ma03.mail.aol.com [172.20.116.47]) by air-ma09.mail.aol.com (v125.7) with ESMTP id MAILINMA093-89e4adb226124f; Sun, 18 Oct 2009 10:12:59 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-ma03.mx.aol.com (v125.7) with ESMTP id MAILRELAYINMA038-89e4adb226124f; Sun, 18 Oct 2009 10:12:51 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1MzWUQ-0002qZ-MK for rs_out_1@blacksheep.org; Sun, 18 Oct 2009 15:12:06 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1MzWUQ-0002qQ-6V for rsgb_lf_group@blacksheep.org; Sun, 18 Oct 2009 15:12:06 +0100 Received: from smtp819.mail.ird.yahoo.com ([77.238.189.19]) by relay1.thorcom.net with smtp (Exim 4.63) (envelope-from ) id 1MzWSq-0003YH-TJ for rsgb_lf_group@blacksheep.org; Sun, 18 Oct 2009 15:10:29 +0100 Received: (qmail 9517 invoked from network); 18 Oct 2009 14:11:47 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=btinternet.com; h=Received:X-Yahoo-SMTP:X-YMail-OSG:X-Yahoo-Newman-Property:Message-ID:From:To:References:Subject:Date:MIME-Version:Content-Type:X-Priority:X-MSMail-Priority:X-Mailer:X-MimeOLE; b=pXu7Kd7aXLW0RELC5dkHBqmoCsv5bJ+PsW+R8l1LRw0Ae4vhVd4Sezb+ubPo+CTENu/GXK2aq5IPkR89C9aYzyAKyjr+oKOm7qhoAkgL0mkXueDQLmMm/1FCudlfm4rYr1xhyyINfzv3cWB2VvrLq2bzJPTzwCYWYggigiCPzDA= ; Received: from unknown (HELO IBM7FFA209F07C) (c.ashby435@86.169.132.116 with login) by smtp819.mail.ird.yahoo.com with SMTP; 18 Oct 2009 14:11:47 -0000 X-Yahoo-SMTP: 9STUSnaswBBSd6nO_2gAC20jmYlWRjmg8d5iYd8s.rl181aR6Sw- X-YMail-OSG: qUwB1MMVM1lYdAlj3M4gxp1nbVZqzWkkOwwbmQCwPdAWBJnQ5XcHuc50p7aSl0ssDcoSR5UZJf3UODwO7q6iCAjSM0lHjC2NghibmbVNt7u56KHyD1TUVUzWUAATp9f5UVAe3bb2HiXb7x0N8t1SRwmXDeFEW0LTeOAeILJmGgS4gR_zqeIbw3F7S27VOwWwzjT3z.N8IL5jolRcNt3ApAf.1LF3pLFH8.abKtvAeqOvp.2LuROcrk4mX8YF1QVVj2VSZ9XpPD_wlYgv0z_p9yNbytdcG3Y- X-Yahoo-Newman-Property: ymail-3 Message-ID: <8FD1DC2A56674846A459F7CD0ADB7468@IBM7FFA209F07C> From: "Chris" To: References: <007201ca4ff9$cce15190$0301a8c0@mal769a60aa920> Date: Sun, 18 Oct 2009 15:11:50 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5843 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 X-Karma: unknown: DomainKey-Status: good (testing) X-Spam-Score: 3.4 (+++) X-Spam-Report: autolearn=disabled,FORGED_MUA_OUTLOOK=3.36,HTML_MESSAGE=0.001 Subject: LF: Re: Re: AF Amps at 136 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0043_01CA5005.51B7A990" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: *** X-Spam-Status: No, hits=3.3 required=5.0 tests=FORGED_MUA_OUTLOOK, FROM_ENDS_IN_NUMS,HTML_30_40,HTML_MESSAGE 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_0043_01CA5005.51B7A990 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Thanks for your comments Mal, I did wonder if such an approach was wis= e. Let's see what others have to say on the matter. I also have my sus= picions about FETs in class D and the level of crud that could result. Thanks again. Chris, G4AYT. ----- Original Message -----=20 From: mal hamilton=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Sunday, October 18, 2009 2:49 PM Subject: LF: Re: AF Amps at 136 Chris=20 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 nev= er worked properly.=20 Read the horror stories of yesteryears about using audio amps for RF= applications. Buckets of burnt out FETS. 73 De Mal/g3kev ----- Original Message -----=20 From: Chris=20 To: RSGB LF Group=20 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 Velle= man 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 =A31= 4.99. 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 modificatio= ns are documented? I guess there's nothing major, reduce a few cap val= ues? Remove Zobel Network etc.?? If anyone has experience with this ap= proach I would appreciate some hints. Thanks. Chris, G4AYT, Whitstable. ----------------------------------------------------------------------= ------ No virus found in this incoming message. Checked by AVG - www.avg.com=20 Version: 8.5.422 / Virus Database: 270.14.20/2443 - Release Date:= 10/17/09 13:08:00 ------=_NextPart_000_0043_01CA5005.51B7A990 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Thanks for your comments Mal, I did= wonder if such=20 an approach was wise. Let's see what others have to say on the matter.= I also=20 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, 200= 9 2:49=20 PM
Subject: LF: Re: AF Amps at= 136

Chris
Do  not use audio amps for RF.= Build a class=20 D or E amp and operate trouble free. Audio amps were tried by some= in the=20 early days but never worked properly.
Read the horror stories of yesterye= ars about=20 using audio amps for RF applications. Buckets of burnt out 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 for= 136kHz,=20 noticed Maplin do a Velleman audio PA kit that is rated at 200W (1= 00W RMS=20 into 4R). OK there's no mains transformer or heat sink, but reckon= it's good=20 value at =A314.99. Point is the specs also say the minus 3db = frequency=20 response is 3Hz / 200kHz.
The RSGB books 'LF Today' refer= to using audio=20 amps as PAs at 136 with 'a few modifications'. Does anybody know= where these=20 modifications are documented? I guess there's nothing major, reduc= e a few=20 cap values? Remove Zobel Network etc.?? If anyone has experience= with this=20 approach I would appreciate some hints. Thanks.
Chris, G4AYT, Whitstable.<= /DIV>


No virus found in this incoming message.
Checked by= AVG -=20 www.avg.com
Version: 8.5.422 / Virus Database: 270.14.20/2443= - Release=20 Date: 10/17/09 13:08:00
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