以改变输入回路的高端谐振频率，使之始终低于本机振荡频率465kHz。所以微调电容C主要用于调整波段高端的接收灵敏度。-To change the resonant frequency of the input circuit of the high-end, so that is always lower than the local oscillation frequency 465kHz. It is mainly used to adjust the trimmer capacitor C-band high receiver sensitivity.