Will have to introduce a system of simple and small FM transmitter. Not only does it meet the requirements of the launch distance, but also at the same time using microphone and voice input signal line, background voice. Modulation circuit surveillance has also joined the table first, so that they can better control and the proper use of transmitters, the following circuit diagram, read briefly, whether it's just like a radio station equipment as many functions. Yes, this small transmitter can help you easily set up an amateur FM radio stations! 500 M in the coverage around. Echocardiography the bar, act immediately!Principle small FM transmitter circuit components and options:
Signal to the microphone after intake, the C1 coupling into the BG1 and external circuit voltage of the single negative feedback amplifier, the voltage signal amplification weak enough to enlarge the extent of U1A and the line to enter the input signal with a mixed U1B. Mixed signal modulation way to the R17 from BG2 FET and the surrounding circuit composed of common than LC finishes the test, the test than the LC oscillator are characterized by a general three-capacitance oscillator simple, but also with high efficiency and high stability. Waveform, and modulation bandwidth, as this amateur production of FM transmitters appears to be particularly important.
Finally BG3 cast by the post-amplifier to enlarge the field by launching antenna fired by general can listen to FM radio broadcast. Another component of the signal through the amplifier to enlarge U1C after the wave rectifier D2 SR DC drive microamps table, Near and surveillance signal modulation rate. Use the system for general should not exceed 85 per cent suitable. GM and other integrated circuits using LM324 four operational amplifier and form a single power reverse input, both of the input voltage is set at half the supply voltage. Table surveillance for the first u-200, BG1.BG3 choose 2SC1815. BG2 three DO2 FET, D2 varactor diode using a S2267. Antenna require the use of 1 / 4 wavelength, such as the use of the best pull rod antenna not less than one metre. Otherwise effect will be less than overstaying launch. Final say about, please do not interfere with normal radio!