Bumped on an interesting article the other day: a cheap power amplifier with two MRF300AN LDmosfets from NXP.
The MRF300 produces about 300 watts @ 50V and operates broadband from 1.8 – 250 MHz. Razvan M0HZH created a little power amplifier with two of these mosfets which put out around 600 watt with 4.5 watt of drive power.
This is a really nice project which is going on my to-do list!
Interesting project. I did some experiments in the past with cheap mosfets from switching power supplies (IRF and IRFP types). In test setup with dummy load there was a lot of power but when the amp was connected to an antenna the amp was very unstable. I would like to see how this amp with MRF300’s behaves when delivering its power to an antenna. So keep on mind, a working prototype on your test bench is not the same as using it on air. Your antenna will have a bad reflection loss compared to the dummy load. Your antenna could also have an inductive or capacitive impedance and the amp will not like this.