What is the basic shape of the waveform produced by a transmitter?

• A. Sine Wave
• B. Square Wave
• C. Triangle Wave
• D. Pulse Train

Answer: (A)

The basic waveform produced by a transmitter is a sine wave, a smooth, continuous oscillation at a single frequency. A sine wave serves as an ideal carrier because its spectrum is very narrow, containing mostly one frequency with minimal harmonics. This makes it easy to amplify cleanly and couple into an antenna, and it provides a stable baseline that modulation can imprint information onto.

Other waveforms introduce extra harmonics or aren't continuous carriers. A square wave has sharp edges, which generate many harmonics and spread energy across a wide bandwidth, making efficient transmission and filtering harder. A triangle wave also contains harmonics but less favorable for a clean carrier. A pulse train is a series of on/off bursts used in some digital signaling, but isn’t the steady carrier waveform; information is typically carried by modulating a sine wave or by switching a carrier on and off in a controlled way.