Abstract: A frequency synthesizer employing direct FM, as opposed to phase modulation, so subaudible tones may be transmitted, in the form of a 10 KHz increment, direct synthesizer with a skewed frequency standard deriving four intermediate 2.5 KHz tuning steps. Fast settling time of frequency change accommodates semi duplex operation, and a shaping network provides the amount of skewing changes required between band ends for substantially perfect tracking. A low division ratio programmed divider in the system maximizes transmitter signal to noise ratio, and a low pass filter in the synthesizer phase locked loop allows voice band moduation.