The small amount of forward bias developed for the PA stage makes it very much easier to drive but is less than the voltage required to actually bias the stage "ON". Keying is in the emitter circuit of the oscillator stage and when the key is up and no current is being drawn there is no forward bias at all on the PA stages.
The isolation of the PA from the oscillator by taking the drive from the low value oscillator collector load, is most impressive and there is virtually no pulling of the oscillator even if the PA load is briefly shorted to ground.
Input to the PA stage runs at 120 to 150mA. at 12 to 14 volts and output on 7Mhz runs at better than 1 watt measured into a 50 ohm load. The PA transistor has a "Stove Pipe" heat sink attached and has been left running continously for more than 1 hour without any complaint from the PA stage.
The collector choke is the usual type and uses 6 turns of 29 swg on two ferrite beads in tandem.
Back to Transmitters Page
Back to Home Page