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?
The movement of the radios loudspeaker membrane is controlled by the deviation of the radio signal from its center frequency. If the station is sending silence the radio signal is still there, just with constant frequency, holding the loudspeaker membrane in a constant position.
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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.
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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.
End of conversation
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