[AMPS] MRF-430 / MRF-157

[Morel Grunberg]

I have  four Motorola RF Power Mosfet transistors MRF-430 and would 
like to built a solid state amplifier. I have some experience with
Motorola
bipolar RF Power transistors ( I've built in the past 300, 500 and 1200W
output HF amplifiers based on Motorola application notes). I still have
a
48V@50A power supply, Cheybishev output filters and a  protection
module ( temperature, currents, overvoltage and SWR ). I have  also a
large aluminium radiator with four quiet fans I used for AN-758 1200W
amp but it's clear that I need a new approach in thermal design for
these
600W output devices.

My basic plan is to use two pushpull modules (each having two MRF-430)
with a splitter / combiner; Vcc=46-48V and only half output of typical
ratings (600-700W for each module instead 1200W). 

I would like to be in touch with anyone having EXPERIENCE in the
following 
areas:

* thermal design and especially PRACTICAL heat transfer methods from
  very small dissipation surfaces
* Motorola application note AR-347 - practical aspects
* the way the IMD can be improved by using four 600W devices for a 
  1200w+ output with at least 36-38dB IMD. 
* output magnetic devices PRACTICAL optimization methods

Please direct answers only, the reflector is busy enough. Also, no need
for comments on $ per W ratio for transistors, it's known already, tnx !

73 de Morel, 4X1AD  


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