618M—2 D是波音707型机的甚高频通信机,通信频率为116MHZ——151.975 MHZ,频率间隔25KHZ或50KHZ,该机为了保证通信的稳定可靠在电路结构上采用了频字式频率合成器。可变分频器是合成器的主要单元电路其电路的结构有许多特点分述如下: 它包括四个同步式分频器即一“ABRS”分频器,“CDEF”分频器、“GHIJ”分频器、和“NO”分频器以串联方式工作。可变分频器的分频范围N=721～1280,分频器最后 618M-2D is a very high frequency communication machine of Boeing 707 type machine, the communication frequency is 116MHZ - 151.975 MHZ, the frequency interval is 25KHZ or 50KHZ. In order to ensure the stable and reliable communication, the machine adopts the frequency-domain frequency synthesizing Device. The variable divider is the main unit of the synthesizer Circuit its circuit structure has many features described as follows: It includes four synchronous divider that an “ABRS” divider, “CDEF” divider, “GHIJ ”Divider, and“ NO ”divider work in series. Variable divider frequency divider range N = 721 ~ 1280, the final divider