Hi,
With the help of few kind engineers, I got some RF power transistors and smaller (in power) is 2N3866. So I have no 'medium' power RF transistor to drive 2n3866. I have 2n3904, 2n4401 but they seems bad with VHF amplifier. I have UHF transistors like S9018, 2n3663, MPSH34 but I know they are just 'signal' transistor and will not drive a powerful 2n3866.

I have KSP10 too. When I saw Fairchild's datasheet, maybe I saw some nice parameter ratings. Then want to ask: can the KSP10 drive the 2n3866 stage (in the case of VHF/UHF amp) and imagine the 2n3866 is biased as class C amplifier.

 

Hi,
With the help of few kind engineers, I got some RF power transistors and smaller (in power) is 2N3866. So I have no 'medium' power RF transistor to drive 2n3866. I have 2n3904, 2n4401 but they seems bad with VHF amplifier. I have UHF transistors like S9018, 2n3663, MPSH34 but I know they are just 'signal' transistor and will not drive a powerful 2n3866.

I have KSP10 too. When I saw Fairchild's datasheet, maybe I saw some nice parameter ratings. Then want to ask: can the KSP10 drive the 2n3866 stage (in the case of VHF/UHF amp) and imagine the 2n3866 is biased as class C amplifier.

The short answer to your question is yes – but looking at the data sheet for the 2N3866 the gain (hfe) can be as low as 5 where a high collector current is used (360mA). The transistor has a lower gain bandwidth (ft) of 400MHz Vs 650MHz for the KSP10 – otherwise one driving the other should be OK.

 

The short answer to your question is yes – but looking at the data sheet for the 2N3866 the gain (hfe) can be as low as 5 where a high collector current is used (360mA).

Does this mean 20mW input will give 100mW output?

And maybe KSP10 pretty nice gain around 100MHz. Am I right if I said the KSP10 is pretty powerful (let's say medium power RF transistor) than S9018 or than MPSH34?

 

Does this mean 20mW input will give 100mW output?

And maybe KSP10 pretty nice gain around 100MHz. Am I right if I said the KSP10 is pretty powerful (let's say medium power RF transistor) than S9018 or than MPSH34?

Electrical power is amps x volts – the gain of a transistor is the current gain.
So if the KPS10 is delivering 70mA to the 2N3866, then it will be able to pass a collector current of 350mA (if its gain is 5).

I suggest you study the data sheets of the transistors in question and compare their operating parameters to answer your question.