The receiver is a direct-conversion VHF FM receiver with phase-locked loop (PLL), implemented by synchronizing the direct frequency of the local oscillator with the received signal.Coil L2 is a local oscillator that operates at a frequency half that of the received frequency. The second harmonic of this local oscillator is superimposed on the signal of the received radio station.The transistor operates as a synchronous detector and as a mixer
The radio receiver is built around a single 9018 transistor. Next comes a single-transistor low-frequency preamplifier and a TDA 2822 audio amplifier. The antenna should be positioned slightly away from the L1/L2 coil. Station tuning is accomplished using a ferrite core. Using a 40 cm antenna, I received signals from approximately eight radio stations. Reception quality is excellent, free of noise and other interference.
First, turn on the receiver without the antenna. Tap the L1-L2 coils with a pencil and you will hear a loud knock from the speaker.
L1=5 turns 5mm
L2=11 turns 5mm
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