555 Fm Circuit Circuit
Posted on May 18, 2012 5796
Circuit for applying a dc-coupled FM or PPM to a 555 configured as an oscillator. IC-1 - Motorola MC-1374P. IC-2 - National LH0002C. L1, L2 - Mouser Electronics #421IF200. C1. C2 - Silver mica, 300 pF. All 0.1 uF cap., ceramic disc, 16V. C3 - 100 uF, 10 V, electrolytic ADJUSTMENT: Adjust R1 for minimum carrier; signal from function generator should generate 500 mVpp at pin 8 of IC-2 (suppressed carrier double sideband). Adjust R2 and function generator level-to achieve 800 mVpp at pin 8 of IC-2 (standard AM with carrier).
Adjust L2 for 455 kHz. Adjust L1 for maximum output.