On a transmitter, a( sends modulated carrier waves into the air.

the answer is antenna

A transmitter is an electronic device which produces radio wave with the help of an antenna. Electromagnetic waves are generated by time varying electric currents which contains electrons flowing through a metal conductor called an antenna which change their direction and thus accelerates. An alternating current flowing in an antenna will create oscillating magnetic field around the conductor.If the frequency of the oscillations are high,the oscillating magnetic an electric field will move away into the air in the form of modulated carrier waves.