Wireless karaoke microphone

(1) Purpose Karaoke is an entertainment way to everyone. A common karaoke method is to insert the microphone on the karaoke machine and sound through the speaker. This production introduction is a simple wireless microphone that receives and enlarges the signal with the FM radio, so it is very convenient, economical, and other applications such as teaching. (2) Basic working principle The frequency modulated frequency range of the FM radio is 88 to 108 MHz. Therefore, the wireless microphone should modulate the sound in this range. The human voice is also known as the audio signal, and its frequency is in the range of 20-20000Hz. When emitting with radio, the audio signal must be placed on the carrier. This process is called radio modulation, and the audio signal is called the modulated signal relative to the carrier. There are two ways, namely, amplitude modulation and frequency modulation, so-called modulation signals to affect the magnitude of the carrier, thereby completing the superposition of the modulation signal and the carrier forming radio waves. The so-called frequency modifier is the frequency of the carrier, thereby completing the superposition of the modulation signal and the carrier to form radio waves. This production is to transmit the human sound through the modulation transmitting circuit of the microphone, and the frequency modulation radio is received. The transmit frequency range of the wireless microphone should avoid the range of use of the local radio station. (3) Technical parameters The transmit frequency of the wireless microphone is 88 to 108 MHz, and the emission distance is not less than 80 meters. Mode emission is transmitted. (4) Determination of circuit selection and components parameters The circuit is shown in the figure. The number of turns from T1 and its peripheral components, the number of turns of the apart, the oscillator frequency can be enabled within the range of 88 to 108 MHz, and a magnifying circuit is composed of T2 and its peripheral components, which is modulated by the preamble. Signal Amba of Ambiguity The emission distance is further reduced to the transmitted state. The sound passed by the pickup and emitted by the antenna. All capacitance CCX series porcelain capacitors, units of PF, 1 / 8W of the electric resistance, φ = 0.51mm induction, φ = 0.51mm induced width, wrapped around 11 turns, transistors, ordinary 9018 I.e. The antenna can be used with a wire for about 60 cm. (5) Production method The printed sheet should be designed to be a long strip, and the purpose is to facilitate placing the microphone. When welding each component accurately, add the power supply, the total current is about 13mA, open the fading sound, tune the frequency of the microphone, then pull the inductance L1, so that the frequency of the microphone is in an appropriate frequency. Pull the microphone and the audio, so that the sound begins to appear well, adjusting L2 to clear the sound reception; then pull away, repeat the above steps until best. In addition, the whole machine needs to be shielded with housing to avoid the external impact caused the microphone running. (Transferred from China Electronic Production Website)

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