RadioBanter - View Single Post - FM Broadcast band as we know it going away?

Pat[_7_] · October 9th 13, 07:36 PM posted to rec.radio.broadcasting

On Wed, 9 Oct 2013 10:17:51 EDT, wrote:

Good day to all of you, guys.

I'm a newbie in communications and I do have some questions I hope you can help me answer. Maybe if you have time, I would really appreciate it.

Thanks in advance!

1. Give 5 other uses of FM broadcasting and discuss how FM is being used.
2. Why do we say that FM stereo broadcasting is using a Frequency Division Multiplexing? Explain.
3. Why is 19 kHz used as the carrier frequency of the FM stereo broadcasting, why not other frequencies?

3 First: FM broadcasts as defined many years ago can handle audio
frequencies much higher than human hearing, but the higher you go, the
more bandwidth is needed. So, you can send ultrasonic audio, but
still want to limit the overall bandwidth. 19 KHz is above normal
hearing, but not by much. Double 19 or 38 is used as the carrier for
the L-R channel. 19 is the pilot frequency, not the carrier. But,
the carrier is exactly twice the pilot. Regarding #2, I suppose some
might refer to it as Frequency Division Multiplexing because the
entire audio bandwidth is divided into different uses. 0 to upper
teens for L+R (monaural), 19 for the pilot. 38 + or - upper teens for
L-R, even higher for other purposes. However, I never heard it called
that. Regarding #1, others will have to answer.