Easy FM wireless microphoneThis FM wireless microphone is easy to build and has a large benefit of transmission (about 300 meters, while outdoor). Regardless of its small component count and 3V operating voltage that will easily penetrate the excess of some floors of an apartment development. It can be adjusted everywhere, while in the FM band (87-108MHz) and its transmissions can be picked up at any ordinary FM receiver. The coil (L1) should be about 3 mm in diameter, with five rounds of 0.61 mm copper wire. You are able Tx frequency range by simply adjusting the distance between the coils. The antenna should be half or quarter of an extended wave (100 MHz 150 cm or seventy-five centimeters).
FM wireless microphone circuit description: The audio amplifier stage (T1) is a conventional common emitter amplifier. The 47nF capacitor isolates the microphone from the base voltage to the transistor and only allows AC signals to pass. The LC tank circuit T2 occurs, the feedback capacitor C5 and the parallel LC circuit L1, C4. The coupling capacitor (C6) directs the signal to your amplifier RF (T3).
FM Wireless Microphone calibration circuit: Location of the transmitter 10 feet of a FM radio. Place the radio in a 89 to 90 MHz Spread the coil in the coil L1 frequency tuning also sought.
