"ff" - yes, I changed to a PNP transistor at the oscillator, to cut out a few parts.
so across L1 to ground the signal should go up to at least 5 or 6 V and then go
down below ground level about the same amount.. and it is a dirty signal waveform,
but it works. .
the way I test all this is to put a 47 to 100 Ohm 2 Watt resistor in the place
of where L2 is in circuit with the IRF510 drain. and also disconnect the output network (L3), and
shunt capacitor (C5). then you can see an almost square-wave across this resistor
going from ground to 12 volts. the IRF510 just needs to be ON about half of the time.
with the circuit all together, for C5, from 470 to 1000 picoFarad is OK...
you can take this part out, for another check, but then there will be a big
flyback voltage spike up to 100 volts or so, and the internal protection Zener
diode will conduct. This will clip out positive going modulation.
and the output power, the load on the IRF510 drain is determined by L3 and C6.
so maybe lower C6 to 680 or 470, and play with L3. add more turns then
spread them out.
I have never had any problems getting 10 watts or more output with this type of
circuit, the flyback mode circuit. I just throw it together and it works.
I have made many like this. I will build
another one as this circuit shows in the next few days or so.
also. measuring the output power... into a 50 Ohm dummy load.
and you have an oscilloscope. look for about 25 to 27 volts going
in each direction (50 to 54 volts peak to peak) that is around 6 to 7 Watts.
just some tips, in case somebody does not know.
after all, this is a "Black Art"
.....