DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws;
  s=s1024; d=btinternet.com;
  h=DKIM-Signature:X-Yahoo-Newman-Property:X-YMail-OSG:X-Yahoo-SMTP:Received:From:To:References:Subject:Date:Message-ID:MIME-Version:Content-Type:Content-Transfer-Encoding:X-Mailer:Thread-Index:In-Reply-To:X-MimeOLE;
  b=KgxRrVXhIo5OwgHvYMhm+MlX5es69NWtcd5imr0WC81mCmq8d3x+NAg0EgZj0c5Mpskx3oL7Lw/oD3HIYPkwNP+udFUqGE4s+9a7Q1al2P6zfO4XS5Olq2RoTaHkhxAU1eQMzvQn16QgtqC4k8fhaFPW7z3zIj8gXJDeJ7bwi64=  ;
From: "Ken" <ken.h.wright@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <4FEB8A2F.3030504@iup.uni-heidelberg.de>
Date: Thu, 28 Jun 2012 11:42:29 +0100
Message-ID: <3B8FD55FDE7A402F9D1C33B7FEF92C09@lindavideo>
MIME-Version: 1.0
Thread-Index: Ac1UtUnxEyZctzULQ1Kh7FZahYfnzgAZS+bg
In-Reply-To: <4FEB8A2F.3030504@iup.uni-heidelberg.de>
Subject: LF: RE: 472 kHz PA running at 12 VDC
Content-Type: text/plain;
	charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
X-AOL-SCOLL-URL_COUNT: 0  
X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-m418.2 ; domain : btinternet.com DKIM : fail  
x-aol-sid: 3039ac1d40cc4fec355676d8
X-AOL-IP: 195.171.43.25
X-AOL-SPF: domain : blacksheep.org SPF : none


Would be much appreciated.

Ken

M0KHW

-----Original Message-----
From: owner-rsgb_lf_group@blacksheep.org
[mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Stefan =
Sch=E4fer
Sent: 27 June 2012 23:33
To: rsgb_lf_group@blacksheep.org
Subject: LF: 472 kHz PA running at 12 VDC

MF,

For the homebrewers, here is my prototype of a MF class D PA that=20
operates at 12 V DC. Input frequency is divided by 4, so a normal HF TRX =

can be used (set to 160m / 1.9 MHz) to drive the PA. The input power=20
must not exceed the range of 1...4 watts. The output power can be=20
switched in 2 steps between ~15W and up to 100W, depending on the output =

impedance and input voltage (10...15V). The output impedance is not so=20
critical, Z=3DR may be in the range of 30 Ohm to infinity. The FETs are=20
IRFZ48N types, the driver is a ICL7667CPA. The transformer uses RF litz=20
wire, 30x0.1mm diameter. I didn't spend to much effort for optimising=20
the efficiency, not at this power level. During a CW QSO or longer calls =

at 50 W RF power the heat sink (which is just a 3mm thick Al plate)=20
becomes hand warm.
The measured efficiency is 88 % at 18W RF power and 80% at 50W RF power. =

The needed power for the driver circuitry is included in this =
measurement.

If someone is interested i may convert the circuit from my mind into a=20
schematic as a png file.

73, Stefan/DK7FC

https://dl.dropbox.com/u/19882028/MF/DK7FC%20472%20kHz%20PA%2015W%2B100W.=
JPG