At 50 watts slightly more efficient than a Valve Class C and at 100 watts
about the same !!
----- Original Message -----
From: "DK1IS" <[email protected]>
To: <[email protected]>
Sent: Thursday, June 28, 2012 10:30 AM
Subject: Re: LF: 472 kHz PA running at 12 VDC
Am 28.06.2012 00:33, schrieb Stefan Schäfer:
> 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
> If someone is interested i may convert the circuit from my mind into a
> schematic as a png file.
> 73, Stefan/DK7FC
me too, please!