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 Board Material: PCB Power Supply: Voltage DC Power Supply 9V2A; The Whole Current 50 to 80mA Frequency: 21MHZ Crystal Frequency Stabilization Adjustment Amplitude: 45% High Frequency Power: 100mW Modulation: Transformer High Potential Modulation Sound Source: External Sound Source, Available Cell Phones, MP3, Computers, etc. Transmitting Distance: Better Than 10m/32.8ft Production Difficulty: Welding, Without Debugging Applicable: 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