A transistor transmitter-receiver unit

Summary form only given. The receiver circuit includes a mixer, oscillator, 3 IF stages, detector, audio stages, beat frequency oscillator and a frequency calibrator. A sensitivity in the order of 1 uv for 10 db S+N/N ratio is attained at frequencies up to 24 mc through the use of a surface barrier transistor in the input circuit. In order to make the relatively sharp IF selectivity characteristic independent of the variations of transistor characteristics with battery voltage and other military surface conditions, an electromechanical filter is employed. Automatic gain control presents an unusual problem since power is required to change the operating point of the controlled stages. By using a reflex-type circuit in the detector sufficient d-c power gain is obtained to realize a 60 db range and a figure of merit of approximately 10 db. The negative-resistance characteristics of point-contact transistors are utilized in the simple divider circuits employed in the frequency calibrator circuits. These follow a 200-kc crystal oscillator and provide an output repetition rate of 5 kc.