3000 meter wireless FM transmitter circuit diagram

as the picture shows. The working voltage is 9V, the working current is 2~6mA. The component parameters can be seen in the figure. BG1 is 9018 and BG2 is C1959 (it can also be 9018, but the power is smaller. If it is D-40, the radiation distance can be expanded to 1000 meters. D -40 is difficult to buy in electronic stores.), L1 and L2 are 0.5mm enameled wire wound around 0.5 round rod 4 and 3 times, the working voltage can be increased to 12V, so the emission distance can be increased, but the frequency will change , the entire circuit is best powered by batteries to achieve the best results in sound quality and frequency stabilization. When debugging, first turn off BG2, adjust the frequency you need, and finally turn on the BG2 circuit to adjust the power. I used BG1--D40 and BG2--C1970 for this circuit and the effect is very good. The voltage is 12V, the working voltage of BG1 is 6V, and the distance is 3000 meters (directional experiment). If you want to use D-40, please note that the working voltage of D-40 is 6V! It is best to install this circuit in an iron box and add a fading reduction network to the input end.