This example describes the use of super-regenerative FM receiver FM receiver principle , the use of high gain microchip , so the circuit is simple novelty . Able to reach the level of the general reception of FM receiver , while overcoming the super-regenerative receiver selectivity , noise and other shortcomings , while maintaining a high sensitivity, low power consumption, low cost and simple lines for the production of electronics enthusiasts . Works novel FM receiver circuit as shown. By the super-regenerative FM receiver , FM AM transform a part of AM detector and the low level circuit. FM wave of super-regenerative receiver is actually converted to the FM wave amplitude waves , while wave amplitude envelope detector to obtain a low frequency signal. FIG transistor VT1 and peripheral components of a typical super-regenerative receiver circuit FM and AM signals into FM wave envelope detection signal, and outputs the audio signal. If R3 selectively removed from the end of the audio signal after the envelope detector is amplified to obtain a relatively large noise in the audio , and the receiver will be deteriorated. Therefore, the present embodiment uses the emitter from VT1 to the sensor through a series circuit of the high frequency signal is then amplitude-modulated high-frequency choke amplified output audio signal detection method to overcome these shortcomings . When VTl work on high-frequency choke will form an amplitude modulated signal FM programs . This signal is coupled to a dedicated receiver AM conducted on micro- wave amplitude demodulation ICI 7642 through transformer T1. This includes the whole process of integrated circuit input impedance level , three high-frequency output amplification and detection , and the gain is greater than 70dB. Audio signal output from the detector is coupled to the capacitor C9 low-frequency transistor VT2 amplified output to the load ( headphone ) listen to the radio through the headphone jack XS. T2 is the effect of preventing high-frequency choke with batteries and other high-frequency signal portion is attenuated to form a loop , but the audio signal but no impediment. Component selection IC1 use 7642 -type wave amplitude demodulation integrated circuit receiving special . VT1 choose 9018 or 3DG142 type and other ultra-high frequency , low noise, low power silicon NPN transistor, requires current amplification factor β> 80, fT ≥ 800MHz; VT2 choose 9013 or 3DG12, 3DK4 silicon NPN power transistor , the current amplification factor required β ≥ 1000 no special requirements other components , according to plans by the standard model and parameter selection. Production and commissioning of small ceramic capacitor C6 tuning capacitor dielectric and asked to take action film in Figure A -side welding, the aim is to reduce the impact on the human body sensors tuning tuning circuit. High-frequency inductors L1 uses Φ1. Omm enameled on this mm round bar around 3 laps bodiless . High-frequency choke transformer T1 with an old AM radio in split out a IFI ' miniature in the weeks around the system, the original wound on the " workers" -shaped magnetic core wire removed, then Φ0.7mm high strength wire rewinding , one side of the high-frequency choke section about 50 laps around the secondary side of the sensing portion of about 150 laps around a regulation coupled with magnetic cap and outer shield can. Selection of high-frequency choke 12 -hole ring, with Φ0. 2mm of wire around each well in 10 laps made . All electronic components mounted on a homemade printed circuit board, and loaded the appropriate size plastic box , power , debugging. By adjusting the first R1 VTl collector current adjusted to 0.3 ~ 0.5mA, adjusting resistor R7 VT2 collector current of about 2mA. At this point you can use headphones to listen to " trace " the sound of flowing water ( electrical noise ) , by adjusting the electrical capacity to listen C6 FM broadcasts . Fine turns from L1 and T1 magnetic cap , so that the best sound volume .
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