Editing Reduced-carrier transmission

{{Short description|AM signal with a low-power or suppressed carrier}}
{{One source|date=August 2022}}
'''Reduced-carrier transmission''' is an [[amplitude modulation]] (AM) [[transmission (telecommunications)|transmission]] in which the [[carrier signal]] level is reduced to reduce [[waste]]d [[electric power|electrical power]].  '''Suppressed-carrier transmission''' is a special case in which the carrier level is reduced below that required for [[demodulation]] by a normal [[receiver (radio)|receiver]].

Reduction of the carrier level permits higher [[Power (physics)|power]] levels in the [[sideband]]s than would be possible with conventional AM transmission. Carrier power must be restored by the receiving [[Radio station|station]] to permit [[demodulation]], usually by means of a [[beat frequency oscillator]] (BFO).  Failure of the BFO to match the original [[carrier frequency]] when receiving such a signal will cause a [[heterodyne]].

Suppressed carriers are often used for [[single sideband]] (SSB) [[transmission (telecom)|transmission]]s, such as for [[amateur radio]] on [[shortwave]].  That system is referred to in full as SSB [[suppressed carrier]] ([[SSBSC]]) or (SSB-SC). [[International broadcast]]ers agreed in 1985 to also use SSBSC entirely by 2015, though [[In-band on-channel|IBOC]] and [[In-band adjacent-channel|IBAC]] [[digital radio]] (namely [[Digital Radio Mondiale]]) seems likely to make this irrelevant.

[[FM stereo]] transmissions use a double-sideband suppressed carrier ([[DSBSC]]) signal from a [[stereo generator]], together with a [[pilot tone]] of exactly half the original carrier frequency. This allows reconstitution of the original stereo carrier, and hence the stereo signal.

==See also==
* [[Carrier recovery]]

==References==
*{{FS1037C}}

{{wikibooks|Communication Systems/Amplitude Modulation}}

{{DEFAULTSORT:Reduced-Carrier Transmission}}
[[Category:Radio modulation modes]]