Stereo encoder circuit explanation

Circuit schematic diagram Y1 and Y2 in IC1-4069 form an oscillator with a frequency of 76KHZ. After Y3-Y6 isolation and shaping, it is sent to a two-component frequency circuit composed of IC2 double JK flip-flop CD4027 to produce a symmetrical /-38KHZ and 19KHZ square wave, of which /-38KHZ square wave is used to control the IC3 analog switch CD4066, switch and modulate the input stereo audio signal, mix it with the 19KHZ frequency signal and then isolate it by the transistor 9014 and send it to the FM modulator. For the FM modulator circuit, please refer to the various FM transmitter circuits in this site.

Connect the FM modulator and the five-volt power supply as shown in the figure, and use a multimeter to measure the pins of IC1CD4069 and the pins of IC2 CP, Q, Q and IC. The voltage should be half of the power supply voltage, indicating that the oscillator has started oscillating. If you have a digital cymometer, measure the output frequency of IC1 and adjust RW1 to make the frequency 75KHZ /-10HZ. If not, adjust the radio first. After RW2 is adjusted halfway, adjust RW1 so that the stereo indicator of the radio is on and there is no temple-frequency whistling sound in the speaker. Then send a stereo audio signal (1.5Vpp, can be output by a power amplifier) from the input, and then you can receive the stereo broadcast on the radio. The input signal can also be obtained from the circuit, but at this time R7 should be changed accordingly. Finally, you can adjust R7 to minimize the high-frequency noise. In fact, R6 and R7 are equivalent to the external components in the 13 and 14 pins of the BA1404. They are a mixed circuit of pilot signals and composite signals, and then input into the amplifier. It is 9014, and BA1404 is entered from 12 feet. I think this circuit has many areas to be improved. If you are interested, you might as well develop it.