Analysis of the results of low-power FM transmitter

(1) to check the printed circuit board and welded, should short-circuit and the imaginary, false welding phenomenon. You can then power. (2) measurement of transistor with a multimeter DC voltage profile V base-emitter asked voltage should be about 7 volts. If the coil L at both ends of a short circuit, the voltage should be some changes, indicating that the circuit is oscillating. (3) Turn on the radio, pull out the radio antenna, the band switch to the FM band (frequency range 88 MHz to 108 MHz) wireless microphone antennas resting on the radio. (4) Slowly turn the radio tuning knob, and transferred to the radio received signal until it clicks. If no signal is received the radio within the tuning range can be stretched or compressed coil L, change its width, and then carefully tuning the radio until the radio to receive a clear signal. And then gradually widened the distance between the wireless microphone and the radio, until a distance of 8 ~ 10m, can still receive a clear signal. Received their own voice in the entire band (88MHz ~ 108MHz), or receive sound effects (not clear or overlap with a radio), indicating that the emission frequency of the FM wireless microphone inappropriate, you can accidentally struck the oscillation coil L, increase or decrease the distance between each turn, and then re-find a station. If not enough, you should remove the coil L, and change its number of turns after welding and try, until the results were satisfactory. Note that the wireless microphone transmitter frequency should avoid debugging Radio frequency within the FM band to avoid interference. (5) transmitting frequency: 100MHz. (6) using the distance: 15M. (7) conditions of use: 3.0V dry batteries, the use of environmental space open, less interference. (8) Operating voltage: 3.0V (9) Test frequency: the number of turns of the inductor 10 100MHz 15 103MHz

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