Let's take Chunlei 40 1 as an example.

BG40 1 is the local oscillator and mixer. B2, C5 and BG 1 form a * * basic oscillator circuit to generate the local oscillator frequency. C2 and B 1 are input loops composed of magnetic rods and capacitors, which receive signals from radio stations.

The 465KHz IF signal generated after mixing is selected by BZ 1 and coupled to BG2 for IF amplification. This machine has only one stage intermediate amplifier, and BG2 is also used for low frequency amplification.

After intermediate amplification, the intermediate frequency signal is selected by BZ2, the secondary signal is detected by D 1, and filtered by R4 and C8. The result is as follows

audio frequency

The signal is sent to BG2 base through C9, C 10 and C 1 1 for audio amplification, and the AC voltage is obtained at R7, and then it is amplified through C 15 to BG3.

The signal of BG3 is coupled from B3 to the power amplifier.

BG4 is a single-tube sliding Class A amplifier circuit, and the static current is small when there is no signal. When there is a signal, the bad voltage coupled by B4 and rectified by D2 increases the working current of BG4 to obtain a larger dynamic range and sufficient power output.