Message-ID: <4BD17701F151495BA7CD01DADE94B67A@standard9dmup1>
From: "Walter Staubach" <wum.staubach@t-online.de>
To: <rsgb_lf_group@blacksheep.org>
References: <4FEB8A2F.3030504@iup.uni-heidelberg.de>
Date: Thu, 28 Jun 2012 12:49:44 +0200
MIME-Version: 1.0
Subject: LF: Re: 472 kHz PA running at 12 VDC
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Stefan,
    me too, pse.
73
Walter DJ2LF

----- Original Message ----- 
From: "Stefan Schäfer" <Stefan.Schaefer@iup.uni-heidelberg.de>
To: <rsgb_lf_group@blacksheep.org>
Sent: Thursday, June 28, 2012 12:33 AM
Subject: LF: 472 kHz PA running at 12 VDC


> MF,
>
> For the homebrewers, here is my prototype of a MF class D PA that 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 must not 
> exceed the range of 1...4 watts. The output power can be 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 critical, Z=R may 
> be in the range of 30 Ohm to infinity. The FETs are IRFZ48N types, the 
> driver is a ICL7667CPA. The transformer uses RF litz wire, 30x0.1mm 
> diameter. I didn't spend to much effort for optimising 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) 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 
> schematic as a png file.
>
> 73, Stefan/DK7FC
>
> https://dl.dropbox.com/u/19882028/MF/DK7FC%20472%20kHz%20PA%2015W%2B100W.JPG
>
>