Tutorials » Other Wireless » Television Basics: Understanding the TV Signal Spectrum

Television Basics: Understanding the TV Signal Spectrum

television signal spectrum modulation vsb

This page provides a television basics tutorial focusing on the TV signal spectrum, detailing both audio and video signal characteristics.

TV Signal Spectrum

As we know, a TV signal comprises two main components: voice (audio) and picture (video). The figure above illustrates the complete TV signal, highlighting both picture and sound carriers. The entire TV signal typically occupies a bandwidth of approximately 6 MHz. As shown in the figure, the sound carrier resides at the upper end of the spectrum, while the picture carrier is at the lower end.

Frequency modulation (FM) is employed to modulate the audio signal onto its carrier. The audio bandwidth usually spans from 50 Hz to 15 KHz. The video signal, originating from the camera, is amplitude modulated (AM) onto the picture RF carrier. The picture carrier frequency is 4.5 MHz lower than the sound carrier frequency.

The video signal can contain frequency components up to 4.2MHz. If both sidebands were to be transmitted fully, it would require a bandwidth of 8.4MHz.

To conserve bandwidth, Vestigial Sideband (VSB) transmission is utilized for the video signal.

In VSB AM modulation, the entire upper sideband is transmitted, but the lower sideband is significantly reduced, thereby saving bandwidth. TV signals are generally transmitted within the 54 to 806 MHz frequency range.