Would like to see more about this. Notice in the 503 schematic that it uses the mosfets in parallel groups (2 on each side of the transformer) more like you would "normally" use a mosfet. I tried building a prototype very similar to this about a month ago, not such good luck, been thinking about it and have some new things to try.
The biggest drawback with the mosfet amps that I have seen so far is:
1. Heat makes them "put out" way less power.... They need to be kept cold for full output
2. They suck at "gain". About 1:3.5 ratio. i.e. You put in 100 watts you get 350-500. not so much if you think in terms of "s-unit" gain. However due to the $price of mosfets, not so bad, ultra cheap power.
I have a pair of Palomar mosfets here and they do rated power. 1 of them I blew the original ERF7530 mosfets... So I went to the cabinets here and found some ultra low gate charge fairly cheap $1.53 each mosfets and stuck them in the Palomar and retuned. It works great so far. Only about 15-20% less power for WAY less money, and I have beat the crap out of these mosfets (decent 400V mosfets) and they have not given out yet. I drive it with 125 watts (it uses 4 mosfets) and it puts out 500-600 watts depending on temperature. What I don't know is how much of it is "on band", I need to send it to someone with a Spectrum Analyzer to see wtf it's doing. I just can't afford a SA right now, times are too tough.... I would like to have one though, and if I did, I'd be doing ALOT of mosfet RF amplifier experiments...
TollFree is right, the Palomars are built in USA and money goes to pockets of americans. RM it goes to Europe, so DO think about that.....
