I found a source of power transistors and decided to try them
using John G4BAO's PCB design which is now public domain. He has
unfortunately , run out of boards so I made my own with a
scalpel to a similar design to test these transistors. results
are very good on the first try - 80 watts saturated 70 watts
P!dB and a gain of 14.4dB , 28 volt supply at about 5 amps @
I am now building another one to test repeatability and if
all is good then I will order some boards and look to selling a
partial kit of PCB, transistor and ATC caps. No Idea of price
Since the supply of reliable MRF286's has dried up , this may
help as a stopgap until another design comes along.
With great thanks to John Worsnop G4BAO for having done all
the hard work in designing the matching and the rest of the PCB.
I won't say yet what device but will let you know soon.
The device used is a MRF5S9070 and I bought them as new old
stock NOS from a UK firm who had them in stock for many years
I will make them available in partial kit form with a PCB
made with Rogers 4350 , power transistor and ATC and C0G
capacitors and when all the development is finished I will write
an article for here and for CQ-TV magazine.
The expected kit price will be £30.00 + postage
See G4BAO amplifier in photos
Email me if you are interested and I will put you on the