Function: 1. The circuit is simple. Only commonly used transistors and resistive capacitive sensing components are used, without the need for an audio transformer, making it easy to manufacture; 2. Good sound quality. Within the rated transmission distance, the sound quality is close to FM radio, with good signal-to-noise ratio, especially when received by a repeater, the effect is not much different from directly playing modulated signals; 4. Multiple interfaces, designed with waveform testing terminals, audio sockets, external power sockets, etc., for easy use and expansion of functions; 5. It can be connected to an external power source and also installed with a battery for independent use. Parameters: Frequency range: 525~1605kHz Supply voltage: 6V DC power interface: 5.5 * 2.1mm Circuit board size: 78mmx85mm (length x width) Transmission distance: about 1 meter for superheterodyne medium wave radio, about 0.5 meters for direct and mineral radio Package includes: 1X module 1X3.5mm headphone signal cable Product Introduction: 1. This kit adopts fully discrete circuit components, which is particularly suitable for students to learn working principles, practice production and testing; 2. Variable capacitors use dual variable capacitors, which are connected in parallel to obtain sufficient capacity; 4. This product has undergone n modifications and improvements so far (mainly modifying the wiring of the circuit board and keeping the circuit unchanged), and is still being continuously improved. Usually minor non substantial modifications, such as slight movement of component positions or adjustments to wiring, will not change the version number, nor will they be re photographed and uploaded. This is hereby declared; 6. The transmitter is equipped with a 3.5mm headphone signal cable, which does not include a battery. Instructions: 1. Insert an external 6V DC power supply (positive inside and negative outside) into the CZ1 socket on the board, or plug the 6V battery pack connector into the Battery interface, being careful not to confuse the positive and negative poles. 2. Insert the signal cable into the CZ2 socket on the circuit board and connect it to the modulation signal source. The signal source can be a mobile phone, player, etc. It is recommended to use a player because mobile phones have strong interference with medium wave radios. 3. Turn the potentiometer knob to turn on the device, which has a similar effect to the volume potentiometer on a radio. 4. Turn on the radio and search for the signal from the transmitter to listen. You can also operate in reverse by adjusting the radio reception frequency to a position without a radio station, and then turning the transmitter dial to change the transmission frequency until the radio plays the signal from the transmitter. Usage restrictions: 2. Increasing the supply voltage can significantly increase the waveform amplitude, but the actual usable transmission distance does not change much; 3. The potentiometer of the transmitter controls the modulation degree. If the modulation is too large, it will cause distortion in the radio demodulation and the waveform of the transmitter itself will also deteriorate.