What does IF mean in an FM circuit?

Answer 1

IF stands for Intermediate Frequency. An intermediate frequency is a frequency which the primary signal or carrier signal signal is changed to in the process of reception or transmission. For example, an FM or frequency modulated radio or FM television tuner uses an intermediate frequency or IF of 10.7 megaHertz, abbreviated mHz. The primary signal of an FM radio may be between 88 to 108 mHz. This signal is processed to 10.7 mHz and then demodulated to an audio signal that human ears can hear. The reason for using an intermediate frequency is that it will not interfere with the primary or carrier frequency. Also, the lower IF frequency is easier to deal with electronically. Commonly used IF frequencies in FM are 10.7 and 5.5 mHz.

AM or amplitude modulation commonly uses 455 kiloHertz although others frequencies may be used.