I found old mosfet transistor IRF843, using 20k and 70k resistor, i manage to set the voltage at transistor gate to 3.9 volt and using 1uF to channel the 27mhz rf signal to the transistor gate, i manage to get an audio from 8 ohm speaker connected to the transistor drain. I'm using about 5.3 volt pow er supply from transformer. The audio is loud and clear. The mosfet gate ca n received from 2v to 4v, as documented in the technical paper.
My actual objective is to amplify the 27 mhz rf to at least 1 watt output. I've seen someone using IRF84x series to get more than 100 watt of rf power , but i wonder why i couldn't do so with this transistor. I replace the spe aker with coil, in hope that some rf signal to be emitted. The rf signal ca me from modulated local oscillator perhaps around 1-3 miliwatts power. It c an be heard in shortwave radio, but not far enough.