Article

Alignment-free FM Detector

This 455-kHz quadrature detector for narrow-band FM signals boasts two important advantages: it is pleasantly simple and it does not require any alignment.The heart of the circuit is formed by the well-known NE612 IC, which is a double-balanced mixer cum oscillator in an 8-pin DIL package.The signal is first buffered by T1 and then fed to the input of the NE612. At the same time, a small portion of the signal is passed to the mixer via a low-value capacitor (C4).

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Materials

014002-PCB.pdf

Gerber file

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PCB

Download Gerber file: 014002-1.zip

Component list

Resistors:
R1,R2 = 560kOhm
R3 = 47Ohm
Capacitors:
C1 = 22nF
C2,C3,C5 = 10nF
C4 = 33pF
C6 = 100pF
C7 = 82nF
C8 = 100nF
Inductors:
L1 = 820µH
Semiconductors:
T1 = BC547
IC1 = NE612AN