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