I think most of these are products inherited when they took over
APT. There's a number of app notes to go with them - they were
originally designed for narrow band saturated cw use and one
common theme is the problems of trying to use them as linear amps.
Bias control is a problem and reduced supply voltage is
recommended, even then linearity is poor. One 'linear' design
quotes IMD as -25dB ref pep or -19dBc!
I dare say they are capable of better than that, but it won't be
simple and straightforward.
Steve
For those interested, MIcrosemi has a line of relatively high voltage
RF MOSFETs:
https://www.microsemi.com/existing-parts/parts/81771
One intriguing possibility with these is direct coupling (through an
LP filter and DC isolation of course) to 50 ohm coax. No transformer
needed.
Something to think about.
73, Bill W6WRT
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