In Reply to: RE: Here's A More Direct Source posted by bwaslo on December 10, 2016 at 19:22:20:
There is no sampling in FM radio.
When broadcasting a stereo (L and R) signal, first the signals are band limited to 15 KHz. Then the modulator forms sum (L+R) and difference (L-R) signals. The L+R signal occupies the lower 15 KHz of the channel. Above that is the pilot tone at 19 KHz. The pilot tone is used to generate a 38 KHz subcarrier, and the L-R signal is amplitude modulated onto the subcarrier, which is suppressed for transmission. No sampling, just AM.
0-15 KHz - Sum (L+R) signal, baseband
19 KHz - pilot tone
23-53 KHz - Difference (L-R) signal, amplitude modulated on 38 KHz carrier
Most FM stations add other services in the remaining channel space between 53 KHz and 100 KHz such as radio for the blind, muzak, RDBS. And then the whole thing is frequency modulated onto the channel's carrier.
This approach allowed for simple & cheap monaural FM radio reception. All you have to do is the one FM demodulation and then filter out anything above 15 KHz.
For stereo FM, you also have to lock on the 19 KHz pilot tone, use it to generate the 38 KHz subcarrier (since the subcarrier was suppressed), demodulate the AM signal, and do another sum & difference to get the left and right signals back.
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Follow Ups
- RE: Here's A More Direct Source - Dave_K 05:38:15 12/11/16 (12)
- RE: Here's A More Direct Source - JURB 15:22:28 12/11/16 (2)
- RE: Here's A More Direct Source - Dave_K 08:36:53 12/13/16 (0)
- RE: Here's A More Direct Source - JURB 15:32:57 12/11/16 (0)
- RE: Here's A More Direct Source - bwaslo 10:19:34 12/11/16 (8)
- RE: Here's A More Direct Source - Bromo33333 11:49:23 12/12/16 (6)
- RE: Here's A More Direct Source - bwaslo 12:17:41 12/12/16 (5)
- RE: Here's A More Direct Source - Bromo33333 14:02:31 12/12/16 (4)
- RE: Here's A More Direct Source - Bromo33333 14:56:33 12/12/16 (2)
- RE: Here's A More Direct Source - JURB 18:23:05 12/13/16 (0)
- RE: Here's A More Direct Source - Dave_K 08:11:37 12/13/16 (0)
- RE: Here's A More Direct Source - bwaslo 14:17:28 12/12/16 (0)
- RE: Here's A More Direct Source - Dave_K 06:11:13 12/12/16 (0)