Ham Radio Extra Class Practice Test

How are analog SSTV images typically transmitted on the HF bands?

1. Video is converted to equivalent Baudot representation

2. Video is converted to equivalent ASCII representation

3. Varying tone frequencies representing the video are transmitted using PSK

4. Varying tone frequencies representing the video are transmitted using single sideband

The correct answer is: Varying tone frequencies representing the video are transmitted using single sideband

Analog Slow-Scan Television (SSTV) is a method used to transmit still images over radio frequencies typically, including HF bands. The correct answer pertains to how these images are encoded and transmitted. In SSTV, varying tone frequencies are used to represent the video signals. The technique involves modulating a single sideband (SSB) signal to carry the video information. Each tone corresponds to a specific pixel value in the image, and by transmitting a sequence of these tones, an image can be recreated on the receiving end. This allows for a relatively simple transmission of images using the available bandwidth in HF communications, where the frequencies are often more limited compared to other bands. The other methods mentioned, such as converting video into Baudot or ASCII representation, are typically associated with text data rather than images. Baudot is a system used for encoding text communications, and ASCII (American Standard Code for Information Interchange) is a character encoding standard mainly used for text as well. Varying tone frequencies in PSK (Phase Shift Keying) primarily apply to different digital data transmission formats, rather than the conventional mode used in SSTV, which is well-suited for single sideband modulation.