Ham Radio Extra Class Practice Test 2025 - Free Extra Class License Exam Questions and Study Guide

In amateur slow-scan television (SSTV), the brightness of the picture is encoded using tone frequency. The SSTV system uses various audio tones to create a visual image, with each tone representing different colors and shades.

The tone frequency is varied to correspond with the different levels of brightness in the image. Specifically, higher frequency tones are used for brighter portions of the image, while lower frequency tones represent darker areas. This modulation allows for an effective way to transmit images, as the frequency variations can be easily detected by receiving equipment.

Tone amplitude typically refers to the strength of the audio signal rather than the brightness of the picture. Sync amplitude refers to the synchronization pulse levels, which are vital for maintaining proper timing between the transmitter and receiver but do not directly influence brightness. Sync frequency involves the timing aspects of the signal synchronization and is not related to how brightness information is conveyed in SSTV.