This is one of my 144Mhz Mosfet amplifiers with Freescale MRF6VP2600H. This is a 49V Ldmosfet amplifier for 144Mhz which easily puts out 500 Watt in linear service.
The amplifier exhibits a gain of around 20dB and noteable gain compression sets in above 500 Watts of output power.
Not shown in the film is a 5 pole low pass filter which was used to reduce the harmonic content of the output power.
The Bird wattmeter uses a 10W slug for full scale. The other wattmeter shows full scale at 2000 Watts.

The gates of the amplifier are shunted to ground with 10 Ohm smd resistors which reduces the gain to 20dB.

First attempts with a 1:4 cable transformer showed good efficiencies as well but gain compression set in too early and not more than 350Watts of linear power could be achieved. That is the reason why I went for a less known 1:9 transformer in the output circuit.

Changing the gate shunting resistors enables me to determine the gain of the stage from 20-23dB.