A frequency-generating system for v.h.f. communication equipment

It is highly desirable to obtain the large number of frequencies required for aircraft communication from a few crystals built permanently into the communication equipment. Besides saving quartz, this leads to higher frequency stabilities and greater flexibility in use than is obtained with the normal practice of separate crystals for each frequency. A frequency-generating system giving 2000 channel frequencies by use of only 32 crystals is described. Selection of a frequency is achieved by simply positioning four switches, the operation of the equipment thereafter being entirely automatic. The system was designed for use in aircraft communication, but the technique is applicable to other multi-frequency requirements at v.h.f. and higher frequencies.