Stefan,
me too, pse.
73
Walter DJ2LF
----- Original Message -----
From: "Stefan Schäfer" <[email protected]>
To: <[email protected]>
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
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