[Mobile-Portable] HF Mobil Amp

[K7fe@aol.com]

The amp I built uses (8) 2SC2879's which are available from a number of 
distributors, such as RF Devices.  100 watts from my Icom 706 is more than 
sufficient to drive the linear amp.  You actually must be careful not to 
overdrive the 
amp by setting the transceiver mike gain too high.  I find that about 50 
watts of drive gives me full power. The transistors are utilized in pairs, 
then 
the pairs are combined using "Wilkinson" type ferrite combiners (twisted pair 
of 
enameled wires with ferrite beads on them or wound around a toroid).  Each 
pair of transistors is biased with it's own variable voltage bias 0.4 to 1.5 
volt supply to provide some isolation between the "pairs."  I have a 12v 
muffin 
fan that blows air over the amplifier heat sink and out the back of the 
shoebox 
size case the amp and bias circuit is built in.  My car is equipped with a 
dual 12v batt system in the car with a 130 amp alternator and of course my 
home 
brew antenna 12 1/2 foot antenna with the 6 inch diameter # 10 wire loading 
coil . 
73, Terry K7FE





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