I have build up the amplifier according to the schematic. And guess what , it worked.
I can get 7 Watt out of it.
No big problems encountered during building. So I continued making lowpass filters.
The work fine in combination with the amplifier. Harmonics are 60 db down.
The amplifier stays stable when the dummy load is disconnected. So far so good. I need to test the amplifier with various load that can occur during tuning.
The amplifier needs 100 milliwatt input.
Then I builded the driver. I need to boost 3-4 mili watt up to 100 milliwatt for the final.
I used a IRF 510 for it.
Now problems start. The signal was distorted and the power is too low.
The biggest problem was the place on the driver output coil were I took the signal.
After fixing it the stability was a problem. fixed that by adding a 47Ohm resistor between the output of the driver and the input of the final.
Finally I got it working. It is stable even without load.It requires less than 2 V pp to get 5 watt out. The third order intermodulation is not that good. The levels are 20 db below carrier using 2 signals 20 KHz apart.
So There is some room for improvement. Problem is in the final. The 3th order intermodulation in the driver is acceptable (-30db)
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