Local oscillator circuit of heterodyne radio

Shown is the local oscillator circuit for a heterodyne radio . In this circuit, cl and Lj form a resonant circuit to select the frequency of the received signal . c5 and L4 form a local oscillator to generate a resonant signal.     When working, the radio signal is coupled through Li and L2 and sent to the base of VT. At the same time, the local oscillation signal generated by c5 and L4 is input to the emitter of VT through C3. The two signals are mixed in VT. The difference frequency signal generated after the frequency is output by the collector of VT, and then in C4, The intermediate frequency signal is selected from the 465 kHz intermediate frequency resonant circuit composed of Ls, and then coupled to the base of the next stage intermediate frequency amplifier tube through k and k for second stage amplification.     The oscillation signal generated by the local oscillator composed of c5 and L4 is input to the base and emitter of VT through C3 and C2, and the amplified signal is fed back to the loop of L4 and C5 through l4 , and then amplified, fed back and amplified , forming oscillation, and the frequency of the oscillation signal depends on the values ​​of L4 and c5.