IF
IF (MF, Medium Frequency), the band from 300kHz to 3000kHz, most of the AM radio. Slightly lower than the frequency is low frequency (LF), slightly higher than the frequency is high frequency (HF). In the daytime, the transmission distance is shorter; but at night time can use the ionospheric reflection signal, can be used for long-distance transmission. But it is easier to mix with other radio signals, affecting reception. ...