给收音机短波段加一个电子微调,将会大大地增加使用的方便性。附图便是采用2CC13A 变容管的调谐器。其它2CC 管均可,不过2CC13A 或 B 较便宜。C_1是隔直流电容,改变 C_1,使其电容量增大,微调频率范围变大,每个台可调范围变小。减小 C_1,则微调频率范围变小,相对而言每个台被展宽。电位器用10k～500kΩ均可,但隔离电阻 R_1不能太小,否则灵敏度、选择性均受影响。外加直流电压小时,2CC 容量大, Adding an electronic fine-tuning to the radio's shortwave will greatly increase ease of use. The figure is the use of 2CC13A varactor tuner. Other 2CC tube can be, but 2CC13A or B cheaper. C_1 is a DC blocking capacitor, change C_1, so that its capacitance increases, fine-tuning the frequency range becomes larger, adjustable range of each station becomes smaller. By reducing C_1, the fine-tuning frequency range becomes smaller, relatively speaking each station is widened. Potentiometer with 10k ~ 500kΩ can be, but the isolation resistance R_1 can not be too small, otherwise the sensitivity, selectivity are affected. Plus DC voltage hours, 2CC capacity,