Posted on Nov 2, 2012 8302
The oscillator, Q1, is a standard overtone circuit. A fifth-overtone crystal, 80.545 MHz, is operated on the seventh overtone, 112.763 MHz. C6 couples the output of the oscillator to Q2, which operates as a doubler to 225.5 MHz. A double-tuned circuit using C7, L2, L3, C10 is used in the collector of Q2 to reduce the level of the 112-MHz dscillator signal. The output of Q2 is capacitivelJ: coupled at C11 to the base of Q3.
The double-tuned circuit in the collector of Q3 with C12, U, L5, C15, is tuned to 451 MHz. A small capacitance, 2. 7 pF, couples the 451-MHz signal to the base of another 2N5179, Q4, which doubles the signal to 902 MHz. The output of the 902-MHz doubler has a triple-tuned circuit using C17, L6, C19, L 7, C20, L8 in its collector.