Return-Path: Received: from rly-mb09.mx.aol.com (rly-mb09.mail.aol.com [172.21.131.167]) by air-mb04.mail.aol.com (v125.7) with ESMTP id MAILINMB043-d2c4adb81bd10; Sun, 18 Oct 2009 16:59:52 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-mb09.mx.aol.com (v125.7) with ESMTP id MAILRELAYINMB098-d2c4adb81bd10; Sun, 18 Oct 2009 16:59:42 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Mzcpz-0004GS-NG for rs_out_1@blacksheep.org; Sun, 18 Oct 2009 21:58:47 +0100 Received: from [83.244.159.144] (helo=relay3.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Mzcpz-0004GJ-6n for rsgb_lf_group@blacksheep.org; Sun, 18 Oct 2009 21:58:47 +0100 Received: from smtp832.mail.ird.yahoo.com ([217.146.189.246]) by relay3.thorcom.net with smtp (Exim 4.63) (envelope-from ) id 1Mzcpm-0004Mf-CR for rsgb_lf_group@blacksheep.org; Sun, 18 Oct 2009 21:58:36 +0100 Received: (qmail 88208 invoked from network); 18 Oct 2009 20:58:28 -0000 Received: from unknown (HELO HughLaptop) (m0wye@86.136.67.92 with login) by smtp832.mail.ird.yahoo.com with SMTP; 18 Oct 2009 20:58:27 -0000 X-Yahoo-SMTP: FrQXuP.swBCnfk4fVWzTzjk6FTteAvBNfSYkM0QPX14MJI8UR8s- X-YMail-OSG: yVKzh60VM1nWHQRKWCTW2zbSd.D5mkp1xuUhznmvjxxe4SpSyoXQ.AGGtoM6Q9kZypBCYxm2J0LNVErcU.NPlf0V8MzmIkVhldodUoQ_v2LtqtUemOSvJCLMP1NNRhWbeFj8ndlooG8dwHavoiweg9iddt.FJIrFvNmfXBQ8lEHlyZXDyV7Jyqxp3ozr_4JzMzkRed8NbGzalS1HVPuXBZMSRVVuOwIAbkJ4MBbAtk0rxlcX90M1M457AaPuNqgkSaduRyxr51qg61z5BZp5odpIJssVZHxs2sDCAQ6y X-Yahoo-Newman-Property: ymail-3 Message-ID: From: "Hugh M0WYE" To: References: In-Reply-To: Date: Sun, 18 Oct 2009 21:58:26 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Windows Mail 6.0.6002.18005 X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6002.18005 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: LF: Re: AF Amps at 136 Content-Type: multipart/alternative; boundary="----=_NextPart_000_006A_01CA503E.1E966E50" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.9 required=5.0 tests=HTML_30_40,HTML_MESSAGE, MISSING_OUTLOOK_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_006A_01CA503E.1E966E50 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hi Chris, I used an OMP 100W amp for my brief sortie onto 136kHz. I never blew= up any FETs, but never managed to get more than 50W out of it either. Unless you want a linear mode go for the switching-on-and-off things= they're much more efficient. Hugh M0WYE ----- 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 Vellema= n 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 =A314.9= 9. 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 wi= th 'a few modifications'. Does anybody know where these modifications= are documented? I guess there's nothing major, reduce a few cap value= s? Remove Zobel Network etc.?? If anyone has experience with this appr= oach I would appreciate some hints. Thanks. Chris, G4AYT, Whitstable. ------=_NextPart_000_006A_01CA503E.1E966E50 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hi Chris,
I used an OMP 100W amp for my brief= sortie onto=20 136kHz. I never blew up any FETs, but never managed to get more than= 50W out of=20 it either.
Unless you want a linear mode go for= the=20 switching-on-and-off things they're much more efficient.
Hugh M0WYE
----- Original Message -----
From:=20 Chris
Sent: Sunday, October 18, 200= 9 2:13=20 PM
Subject: LF: AF Amps at 136

Hi All,
Just started constructing TX for 13= 6kHz, noticed=20 Maplin do a Velleman audio PA kit that is rated at 200W (100W RMS in= to 4R). OK=20 there's no mains transformer or heat sink, but reckon it's good valu= e at=20 =A314.99. Point is the specs also say the minus 3db frequency= response is=20 3Hz / 200kHz.
The RSGB books 'LF Today' refer to= using audio=20 amps as PAs at 136 with 'a few modifications'. Does anybody know whe= re these=20 modifications are documented? I guess there's nothing major, reduce= a few cap=20 values? Remove Zobel Network etc.?? If anyone has experience with th= is=20 approach I would appreciate some hints. Thanks.
Chris, G4AYT,=20 Whitstable.
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