Because the PA has both shunt feedback and emitter degeneration, the choice of transistor is not critical. I have had good results with a Motorola 2N6367 and a Mullard/Phillips BLW60. For output levels of less than 5 Watts, a CB output transistor would be suitable. Adjust the value of the 15 Ohm resistor to set the standing current. The DC input power should always be more than twice the peak output power. You will need a good heatsink. I left the transmitter running for fifteen minutes, while I was doing some two tone tests. The PA heat sink was too hot to touch!
The 82 Ohm resistor is a 2 Watt carbon resistor, NOT wirewound. The 1 Ohm resistors are 1 Watt carbon. For the input transformer, I used a pair of 4:1 transmission line transformers to give a 16 to 1 impedance transformation. Each transformer is 4 turns, bifilar wound on a high permeability ferrite core. The output transformer is a conventional broad band transformer with a ferrite core. The primary is a single turn, made from two lengths of brass tubing and the PCB end plates. The secondary is three turns, threaded through the brass tubes.
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