AM and FM modulation

A

ahmedragia21

Member

• Feb 13, 2008

• #1

Hi, I wonder why AM is used for transmitting Picture signal in TVs and FM for transmitting Audio Signal..

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• Feb 13, 2008

• #2

I suggest you study how TV works then?, in particular bandwidth requirements and Vestigal SideBand reduced Carrier. Also look up intercarrier sound.

Where more bandwidth is available (on analogue satellite) FM is used for the picture.

 

A

ahmedragia21

Member

• Feb 13, 2008

• #3

I read that in my book,FM is used for audio signals because of low bandwidth , and AM for picture because it has a high bandwidth , how come then ? . If AM is better why i didnt use it for sound also like picture ? that's my question...

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• Feb 13, 2008

• #4

That's the wrong way round, FM takes up a LOT more bandwidth, which is why AM was used - and check the other part of my previous post about VSB.

Incidently, the original UK TV (the first in the world) used AM sound as well, and lasted until the 1980's or so?.

 

O

on1aag

New Member

• Feb 13, 2008

• #5

Hi Ahmedragia21,

Nigel forgot to mention that in a television transmitter one sideband
is almost completely suppressed.
They can do that because both side bands contain the same information.
By doing so they reduce the bandwith to almost 50 %.

on1aag.

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• Feb 13, 2008

• #6

on1aag said:

Hi Ahmedragia21,

Nigel forgot to mention that in a television transmitter one sideband
is almost completely suppressed.

Click to expand...

No, I mentioned it - VSB reduced carrier.