Electronic – Do commercial AM radio stations broadcast a carrier

radiotransmitter

A possibly dumb question: I'd like to know if commercial AM radio stations broadcast a carrier tone along with signal sidebands. To ask my question is a different way; if I could measure (view) the spectrum of a transmitted commercial AM broadcast signal presumably I'd see the two symmetrical sidebands' spectral energy. But would I also see a single narrowband spectral component, a carrier tone, in the center of the two sidebands? (I've searched and searched the Internet trying to find out if commercial AM broadcast signals are suppressed-carrier AM signals. But I've found no clear answer.)

Best Answer

AM broadcast stations do exactly that: broadcast AM. Not single sideband, double sideband with suppressed carrier, or anything else. That means a carrier in the middle and a sideband on each side.

The fact that the carrier is a significant component of what is transmitted should also be obvious from a few seconds thought. By definition, AM changes the amplitude of a carrier to encode the baseband signal. At full or 100% modulation, the carrier amplitude varies between 0 and some maximum, with half that value being the average. Obviously there is significant carrier component in the result.