Frequency conversion circuit, oscillation and mixing together referred to as the inverter circuit. Frequency conversion tx1 circuit based on VTl as the center, its role is to through the different radio frequency signal input circuit receives (high frequency signal) to transform the fixed intermediate frequency signal of rxb9 465 KHZ. VTl, T2, CB and other components of the local oscillation circuit, its task is to produce a constant amplitude is higher than the input signal frequency, 465 KHz high frequency tx1 oscillation signals. Due to Cl quite short circuit with high rxb9 frequency signal, Tl and inductance of the secondary Lcd is small, provided the pathway of the high frequency signal, so the local oscillation circuit is common base circuit, oscillation frequency controlled by T2, cB, cB is double the other in a row of the capacitor, adjust it to change the local tx1 oscillation frequency. T2 is oscillation coil, the first round on the same core, they are magnified the VT1 electrode, such as the output of the coupling oscillation signal in the form of positive feedback to the oscillator circuit, rxb9 voltage from the T2 primary tap local oscillation, derivation by C2 coupled to VT1 emitter.

Mixing circuit is composed of VTl, T3's primary coil and so on, is the common emitter tx5 circuit. Its working process is: (magnetic antenna receiving radio signals) through input circuit, rxb12 received radio signal to VTl by Tl secondary coil Lcd of the base, and the local oscillation signal tx5 sent by the C2 to VTl and emitter, the two frequency signals in rxb12 T1 mixing, due to the effect of nonlinear of the transistor, the result of the mixed to produce various frequency signal, one is the local oscillation frequency and radio frequency difference is equal to 465 KHZ signal, that is the intermediate tx5 frequency signal. Mixing circuit load is medium frequency transformer, T3 primary coil and internal capacitance of parallel resonant circuit, the resonance frequency is 465 KHZ, can put the 465 KHZ of intermediate frequency signal to choose from a variety of rxb12 frequency signal, and through the secondary coil of T3 coupling to the next level, and other signals are almost filter out.

Intermediate frequency amplifier circuit, mainly composed of rxb8 VT2, VT3 two levels of intermediate frequency amplifier. First put in the circuit VT2 load is medium frequency transformer rxb10 of T4 and internal capacitance, they form parallel resonant circuit, rxb8 resonance frequency is 465 KHZ, compared with the direct put the radio described above, the superheterodyne receiver sensitivity and selectivity are much improved, the main reason is that with the intermediate frequency rxb10 amplifier circuit, it is more easy than high frequency signal tuning and magnified. Detection and automatic gain control circuit, the intermediate frequency signal by rxb8 level of intermediate frequency amplifier fully enlarged by T4 coupled to the detector tube VT3, VT3 amplification effect already, and detecting tube, VT3 triode in the composition of the detection circuit, the circuit detection efficiency is high, has the strong rxb10 automatic gain control (AGC).

The AGC control voltage by R3 to VT2 is the base, the control process is: Outside rxb11 signal voltage and write Vb3 write - Ib3 - the Ic3 write - vc33 left, by R3, Vb2 left - > Ib2 left - > Ic2 left left - > tx3 signal voltage. The detection level is the main task of the intermediate frequency modulation rxb11 signal back into audio signal, C4, C5 filter to the remnants of the role of intermediate frequency components. Lead low circuit, detection of audio signal after filtering by potentiometer RP to lead low pipes VT4, through low voltage amplification dozens to hundreds, tx3 audio signal but audio signal after amplification on load ability is very poor, rxb11 also can not directly promote the speaker work, power amplifier is also required. Rotating potentiometer RP can change VT4 base on the size of tx3 signal voltage, can achieve the purpose of the control volume.

Input circuit is composed of double variable rxb3 capacitor of CA and T1 Lab primary coil, a parallel resonant circuit, Tl is magnetic antenna of rxb15, from the antenna in the high frequency signal, through the input circuit resonance choose need radio signal, radio frequency signal is f = l / 2 PI LabCA, when change the CA, will be able to receive radio signals of different frequency. Power rxb3 amplifier (OTL circuit), the task of the power amplifier is not only the output voltage, and can output the larger current. This circuit USES no power amplifier output rxb15 transformer, can eliminate the distortion of the output transformer caused and loss, good frequency characteristic, can also reduce the volume and weight of the amplifier. VT5, VT6 push-pull circuit, of the same type transistor R7 and R8, and R9, R10 VT5, VT6 deviator resistance. Do inverter coupling transformer T5, C9 is blocking capacitance and coupling capacitance. In order to reduce the rxb3 frequency distortion, the better the greater the capacitance C9 selected. No output transformer of power amplifier's output impedance rxb15 is low, can drive a speaker work directly.