1、SOUND AMPLIFICATION: R2, R3 for the sound source access resistor SW1 volume potentiometer, IC1 sound amplifier chip, C9 sound coupling capacitors, C11, C12 sound bypass capacitors, R1, C8 RC filter circuit, R5, D1 power indicators. 2、OSCILLATION SOURCE: Q1 consists of a common base modulation transformer oscillation circuit, generating high frequency equal amplitude signals, adjusting the CV can be set at a frequency of 530‑1600KHZ, R10, C19 for the positive feedback network, C18 for the high frequency bypass capacitors, so as to achieve a common base and the circuit, C16 power supply filtering and high frequency bypass, C17 power supply filtering; R7, R8, R9 for the bias resistor. 3、HIGH FREQUENCY AMPLIFICATION: Q2 Q1 high frequency amplitude signal further amplification, C20 for the coupling capacitance, C21 high frequency bypass capacitance, R11, R12 for the bias resistor, B2 for the high frequency broadband conduction inductance. B2 secondary output high frequency voltage. 4、HIGH FREQUENCY MODULATION: C22, C23 sound capacitors, adjust SW3 to get the right sound voltage, R15 negative feedback resistor, SW2, R14 bias resistor, adjust SW2 can improve the sound quality. 5、FILTER NETWORK: L2, L3, C26, C27 for the low pass network, filter out the high harmonics, so that the waveform is close to sinusoidal, matching the antenna. Item Type: Radio Medium Wave Transmitter Kit Material: PCB Power Supply: 9V2A DC, 5.5 Interface, Internal Positive and External Negative (Need to Provide Their Own Power Supply) Transmission Frequency: 530‑1600KHZ (Radio Medium Wave Band) HF Transmitting Power: Adjustable 20‑500 MW, Adjust The Power in 5‑10 Meters to Use. Antenna: 1.5 Or 2.5 Square Millimeters in Diameter Household Wire Can Be Used, with A Length of 2‑5 Meters (Need to Be Self Provided) Sound Input: 3.5mm On Both Ends, Comes with Board Accessories Sound Source: CD, Desktop Computer, Cell Phone, Etc. Applicable: Medium Wave Radio Enthusiasts, for Students to Study Wireless Signal Generation, AM Transmitter Sound Modulation Principles. 1 x Transmitter 1 x Screw Package 1 x Instruction Manual 1 x Sound Cord