85 MHz oscillator driving 50 ohms at 6 watts.

I need a low cost 85 MHz source (sine wave) to drive a 50 Ohm load at about 6 watts. Something off the shelf would probably be too expensive; I want to build or find something cheap. Off hand I'm thinking a crystal or VCO driving an simple RF amplifier is doable but not sure if it will require a PCB layout (versus a protoboard) to avoid noise issues. Any suggestions?

Why so cheap.

I would do a mosfet set up as an oscillator with an LC tank as the resonator. Maybe S5 when you are done.

Cheap because the professor I'm helping has little grant money and doesn't want to spend it on electronics. So cheap he is scrapping the old circuit and keeping the shielded box. Thanks.

biff44's idea would be very effective for a simple oscillator (cheap, simple, but not super-easy to tune or accurate over wide temp range, etc). If it needs to be hardier, then you'll have to increase the complexity (and cost/time). Follow it up with one (or two) gain stages and viola!

As for protoboard vs. PCB, you'll pretty much need a PCB. 85 MHz could be really tough to tune with the monstrous amounts of parasitic capacitance on spring-finger-like protoboard. I don't recommend them much above a few MHz (too many variables to fight with while tweaking a new design).

Dear lsuphysmn
Hi
You can design a simple self exciting oscillator with this frequency , and after that , a simple class C amplifier , to make that power .
Best Wishes
Goldsmith