Fail to amplify 27mhz rf using mosfet IRF843

idzuan · 2017-03-17T05:02:16+00:00

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.

Mar 17, 2017 20 Replies

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Tim Wescott 9 years ago

Yup. Now that I have time to think back far enough, people were getting reasonable amateur-radio type performance out of those things in the 80 meter (3.5MHz) band -- but that's a hair lower frequency than 11 meters.

Should be good suitable parts from DigiKey or Mouser, if he's in the US.

Tim Wescott Control systems, embedded software and circuit design I'm looking for work! See my website if you're interested http://www.wescottdesign.com

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