The previous post about he 10W Amp is at: QRP Labs 10W Linear Amp (1)
Mike, KA5VZE, assembled the 10W amplifier and delivered it to me, the other brother, KG5KCW, yesterday. After carefully setting the idle current in the finals to 125 mA per transistor, I drove the amp with a signal generator into a dummy load. The amp seems to work as promised. I only tested at 7030 kHz.
Measurements:
Input voltage: 3.48Vpp
Output voltage: 64Vpp
Voltage gain: 18.4 V/V, or 25.3 dB (kit gain spec is 26 dB)
Next step is to design and build low pass LC filters for 40 and 20 meters.
We may also need a booster for the frequency synthesizer circuit we'll use to drive the amp with.
The test setup is shown below. Outside the picture is a 25W 50 ohm dummy load.
Photo below shows the signal generator setup. The generator is set at 4.2V but the voltage at the input to the amp is 3.48V, this calculates to an amp input impedance of 244 ohm.
Photo below shows the test results on the oscilloscope. The calculated gain is given above. The output power is 10.4W. The input current to the amp is 2.36A @ 12V, input power is 28W and efficiency is 37%.
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