Feature:1. Application: This is a short wave transmitter, mainly used in short wave radio experiments and tests, understand the principle of AM modulation.2. Structure: Mainly consists of power input, sound amplification, sound modulation, 21MHZ high frequency oscillation, Class C high frequency amplification, 21MHZ low pass filter.3. Power Input: Professional AM radio transmitter board, C1 to C6 for the filter capacitors, reduce the power supply interference ripples.4. Sound Modulation: Transformer B1 secondary inductance sound voltage superimposed on the DC power, to get the modulation voltage with the change of the sound source.5. High Frequency Oscillation: 21MHZ high frequency oscillation, crystal Y1 in the circuit is a parallel resonance, equivalent to the inductor.Specification:Item Type: AM Radio Transmitter BoardMaterial: PCBPower Supply: Voltage DC Power Supply 9V2A; The Whole Current 50 to 80mAFrequency: 21MHZ Crystal Frequency StabilizationAdjustment Amplitude: 45%High Frequency Power: 100mWModulation: Transformer High Potential ModulationSound Source: External Sound Source, Available Cell Phones, MP3, Computers, etc.Transmitting Distance: Better Than 10m/32.8ftProduction Difficulty: Welding, Without DebuggingApplicable: Radio Enthusiasts, Students Experimental Testing.Package List:1 x AM Radio Transmitter Board 1 x Screw Package 1 x Instruction Manual 1 x Sound Cable 1 x Antenna