ARRL Technician Practice Exam

What is the typical bandwidth of analog fast-scan TV transmissions on the 70 cm band?

1. 1 MHz

2. 3 MHz

3. 6 MHz

4. 10 MHz

The correct answer is: 6 MHz

Analog fast-scan television (TV) transmissions on the 70 cm band typically occupy a bandwidth of about 6 MHz. This specification arises from historical practices in analog television broadcasting, where standard video signals were designed to fit within this bandwidth to ensure quality transmission without excessive interference. When considering the characteristics of analog fast-scan TV, it utilizes a video signal format that requires a broader bandwidth compared to narrower modes of operation such as voice communication. The 6 MHz bandwidth allows for the transmission of the video and sufficient audio signals while maintaining good picture resolution and clarity for viewers. In contrast, the other bandwidth options—1 MHz, 3 MHz, and 10 MHz—do not align with the standardized needs of analog fast-scan TV. A bandwidth of 1 MHz would be insufficient for a decent quality video signal, while 10 MHz is larger than what is typically necessary for these types of transmissions. As such, 6 MHz is recognized as the correct choice for analog fast-scan TV in the 70 cm band due to its balance of quality and efficiency in spectrum usage.