New FM receiver, FM Receiver
Keywords: FM receiver production
This article describes the principles of ultra-regenerative frequency modulation reception, because the circuit is simple and novel in the high gain micro integrated circuit. The receiving effect reaches the level of the general faster receiver, and overcomes the advantages of the ultra-reproducing receiver selective poor selectivity, noise, and maintains high sensitivity, less power consumption, simple lines, and low cost (less than 5 yuan for component costs). Suitable for electronic enthusiasts. Composed of ultra-reproduced frequency modulated, FM-AM conversion portions, amplitude detection and low amplifier circuit. The ultra-regeneration reception of the modulated frequency wave is actually converted to a split wave while the amplitude wave is enamded to obtain a low frequency signal. The triode VTL and peripheral components in the figure form typically ultra-reproduced frequency modulated circuits, and converts the modulated wave signal to a modulation signal and perform envelope detection output audio signals. If the audio signal after the envelope detection after the R3 is taken directly, the resulting audio noise is relatively large, but the selectivity of the receiver is deteriorated. Therefore, the method of high frequency amplifier, detection output audio signal is used to overcome the above-mentioned deficiencies in the high-frequency choke in the high frequency choke in the high-frequency choke in the serial circuit. When VT1 works, a modulation signal modulated by the FM program is formed on the high frequency choke circle. This signal is coupled to the demodulation of the modulation wave on the modulation dedicated receiving micro IC1 7642 by the transformer T1. This integrated circuit contains the whole process of primary high-resistance input, three-stage high frequency amplification and detection output, and the gain is greater than 70dB. The audio signal of the detection output is coupled to the triode VT2 by the capacitor C9 to perform low frequency amplification, and outputs it to the load (earphone) to listen to the broadcast program by the headphone socket CZ. High frequency choke coil T2 is to prevent high frequency signals from being attenuated with the battery and other portions, but the audio signal has no obstacles. Capacitor C6 is a small porcelain fine-tunable capacitor, and the movable sheet is required to connect the movie in the A end of the figure in the figure, and the purpose is to reduce the impact of the human body induction on the tuning circuit during the stage. The high frequency inductance L1 is formed from a thick rod of φ5.0 mm from a rod of φ5.0 mm. The high-frequency choke induvers T1 uses the AM-IFT micro-medium surrections removed from the old machine to remove the paint line of the lacquer line of the "work" shape magnetic core, and then use φO.07mm high strength enamel line Winding, the primary high-frequency choke portion is about 50 laps, and the secondary induction portion is adjusted to adjust the magnetic cap and the outer shield from about 150 laps. The high frequency choke t2 is selected from the respective holes in each well with a double-hole magnetic ring, which is made of 10 turns in each well with φ0.2 mm. First adjust R1, the collector current flow of VT1 is 0.3 mA-0.5 mA, and the adjustment resistor R7 causes the collector current of VT2 to 2 mA. At this point, "silk" can be listened to the "wire" water rang (electrical noise) by adjusting the capacitance of C6 to listen to the broadcast program of the frequency station. The l1 匝 and T1's magnetic cap are fine, and the sound quality volume is best.
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