Every day in the USA you can hear stations broadcasting using double
sideband - suppressed carrier -- what are these/

--
CL -- I doubt, therefore I might be !

Caveat Lector wrote:
Every day in the USA you can hear stations broadcasting using double
sideband - suppressed carrier -- what are these/

If they're military, they might be sending two (or four) independent
data streams. Think RTTY.

--
Mike Andrews, W5EGO

Tired old sysadmin

The USA FM band uses double side band suppressed carrier as follows

1.. The first is a normal audio signal made up of the Sum of the left and
right channels. This is the signal you hear on a Mono radio and is the same
as switching the Stereo/Mono Switch on an amplifier to "Mono'.
2.. In addition a difference signal (Left - Right) is generated and then
used to modulate a 38 Khz subcarrier using Double sideband suppressed
carrier (DSBSC) modulation. This is an AM modulation of the subcarrier.
3.. To keep the receiver decoder locked into the 38Khz subcarrier a 19 Khz
pilot tone (EXACTLY 1/2 of 38 Khz) is transmitted at well. The relative
percentage of modulation put into the pilot is 10%.

--
CL -- I doubt, therefore I might be !






"Mike Andrews" wrote in message
...
Caveat Lector wrote:
Every day in the USA you can hear stations broadcasting using double
sideband - suppressed carrier -- what are these/

If they're military, they might be sending two (or four) independent
data streams. Think RTTY.

--
Mike Andrews, W5EGO

Tired old sysadmin

Caveat Lector wrote:
Every day in the USA you can hear stations broadcasting using double
sideband - suppressed carrier -- what are these/

FM broadcast stations -- but only if you're listening in stereo.

(the L-R channel is broadcast DSBSC on a 38KHz subcarrier on the main FM
signal)

(the same stereo method is, to my knowledge, used worldwide)
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

"Doug Smith W9WI" wrote in message
...
Caveat Lector wrote:
Every day in the USA you can hear stations broadcasting using double
sideband - suppressed carrier -- what are these/

FM broadcast stations -- but only if you're listening in stereo.

(the L-R channel is broadcast DSBSC on a 38KHz subcarrier on the main FM
signal)

(the same stereo method is, to my knowledge, used worldwide)
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

Very good Doug
Don't know if the scheme is used world wide - good question
Maybe others can confirm

As a second quiz -- what other information is transmitted besides the main
R+L, 38 kHz DSBSC, and 19 kHz pilot carrier ?

On Thu, 6 Oct 2005 07:21:02 -0700, "Caveat Lector"
wrote:



"Doug Smith W9WI" wrote in message
...
Caveat Lector wrote:
Every day in the USA you can hear stations broadcasting using double
sideband - suppressed carrier -- what are these/

FM broadcast stations -- but only if you're listening in stereo.

(the L-R channel is broadcast DSBSC on a 38KHz subcarrier on the main FM
signal)

(the same stereo method is, to my knowledge, used worldwide)
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

Very good Doug
Don't know if the scheme is used world wide - good question
Maybe others can confirm

As a second quiz -- what other information is transmitted besides the main
R+L, 38 kHz DSBSC, and 19 kHz pilot carrier ?


Didn't it once include a subcarrier to allow the use of
elevator/background music for equipment rented by subscibers to the
service?

How about the kind of info displayed on digital receivers for
stuff like station id, station type and the like?

--
CL -- I doubt, therefore I might be !






wrote in message
...
On Thu, 6 Oct 2005 07:21:02 -0700, "Caveat Lector"
wrote:



"Doug Smith W9WI" wrote in message
...
Caveat Lector wrote:
Every day in the USA you can hear stations broadcasting using double
sideband - suppressed carrier -- what are these/

FM broadcast stations -- but only if you're listening in stereo.

(the L-R channel is broadcast DSBSC on a 38KHz subcarrier on the main FM
signal)

(the same stereo method is, to my knowledge, used worldwide)
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

Very good Doug
Don't know if the scheme is used world wide - good question
Maybe others can confirm

As a second quiz -- what other information is transmitted besides the
main
R+L, 38 kHz DSBSC, and 19 kHz pilot carrier ?


Didn't it once include a subcarrier to allow the use of
elevator/background music for equipment rented by subscibers to the
service?

How about the kind of info displayed on digital receivers for
stuff like station id, station type and the like?

Yep some stations transmit in the subcarrier set such
things as digital or analog SCA (Subsidiary Communications Authorizations)
or RDS signals. these are carried in most cases on 76 and 92 KHz
subcarriers, although there is no steadfast rule for use of subcarrier
frequencies, only convention.

SCA at URL:
http://www.blackcatsystems.com/radio/sca.html

RDS at URL:
http://electronics.howstuffworks.com/question323.htm

CL

Caveat Lector wrote:
As a second quiz -- what other information is transmitted besides the main
R+L, 38 kHz DSBSC, and 19 kHz pilot carrier ?

Not necessarily anything. But optionally:

67KHz subcarrier
92KHz subcarrier
(previous two generally used for background music, data broadcasts,
narrowcast talk, or reading services for visually-impaired)
(a 41KHz subcarrier was also popular back before virtually all stations
went stereo. 41KHz SCA is not compatible with stereo.)

57KHz R(B)DS data subcarrier

Other subcarriers are possible but these are the standards for which
off-the-shelf equipment is available.

Also possible is an IBO(A)C digital signal which occupies the guard
bands at the edges of the station's channel and the adjacent channels on
either side.
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com