EXPLAIN LIKE I’M MODERATELY INTELLIGENT: - You tune FM radio to a dead channel, it’s loud static. - You turn FM radio to an active channel playing silence, it’s quiet. Is this ONLY because of automatic gain control, or is there a more complicated reason?
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very succinct. good explanation. tuning to a dead channel causes the tuning circuit to boost ambient (white) noise. a broadcast of a silent signal has a carrier which is far enough above the noise floor to "lock". FM broadcast of a silent source looks like a perfect sine wave.
Thanks. It's of course an oversimplification, because all modern FM broadcasts are stereo. So you'd always have the stereo sub-carrier modulating the signal. But an old-school mono broadcast would indeed be a perfect sine wave when they transmit silence.