The AM Forum

I guess using switching FETs in saturation is out because of the gate capacitance at 10 meters. A FET designed for linear service would have to be used and biased somewhere below saturation.

I'm thinking about using analog drive from a ricebox to drive the gate. I'm thinking maybe 10 watts of drive and then use a little DC on the gate to bias it in class C. I already have another huge transformer to Heising modulate.

I found an old networking enclose box at a thrift store (imagine an enterprise grade switch) with no holes on the front. On the back where all the factory chassis openings are, I bolted over with a piece of 1.5" steel. Then I painted it all black. It looks really nice and fits neatly below my computer monitor. I think it would make an excellent transmitter.

Jon
KA1TDQ

Well Jon if you won't go tun saturation I would apply these Mosfets:
BF548 or the free scale  counterpart was do the same output power.
To spare some enormous modulation power, I would advise to modulate these devices in class AB where they mean't before.

73"

I guess I thought to see a crystal and MOSFET, how interesting that might be if it would work and make any real juice. Sort of like the old crystal+6L6..

Still this is really interesting to see what drive might be required and how its done. It's good learning for me!

I have a 1x1 rf deck pwm at 10 meters.   It runs from 10 to 12 fairly decent.

It takes about 3/4 Watt carrier and produces to 200 watts pep.


I can supply you with part numbers of fets I've successfully tried,  if it will help.   Notes are in the garage,  of course.

And I use sinewave drive on most as well.

--Shane
KD6VXI