hi
i built this attached amplifier circuit 10w @3.1 MHz it works well on 1mhz, couldn't make it work on 3mhz from my function generator. yes i used normal poly capacitors not mica, any ideas? the coil was made with the help of Nanovna to measure inductance.

 

What does it do with 3MHz input?

 

What does it do with 3MHz input?

Nothing. 0w output

 

Nothing. 0w output

That seems unlikely. Did you check the signal in the gate?

Where did the circuit come from? That appears to be a class C amp, and will only amplify if the input goes above the MOSFET’s threshold, which is 4 volts.

 

That seems unlikely. Did you check the signal in the gate?

Where did the circuit come from? That appears to be a class C amp, and will only amplify if the input goes above the MOSFET’s threshold, which is 4 volts.

That seems unlikely. Did you check the signal in the gate?

Where did the circuit come from? That appears to be a class C amp, and will only amplify if the input goes above the MOSFET’s threshold, which is 4 volts.

this circuit is driven by function generator @ 10v or more

 

What the function generator claims is not important. The question is what is the voltage on the gate. Do you have a scope?

 

Bob made a good point that slipped right by. And look at the specs for the IRF510 switching transistor. There are a bunch of picky conditions required to make a mosfet amplify. In addition, putting out ten watts at 3.1 MHZ may attract a professional team of RDF folks who are not easily amused.
(RDF=Radio Direction Finding.)