ISB is a type of what in radio communications?

• A. Encryption method
• B. Sideband transmission
• C. Power supply
• D. Antenna tuning

Answer: (B)

Independent Side Band is a form of sideband transmission. In radio modulation, information is carried by the sidebands that appear around the carrier. Traditional AM uses both upper and lower sidebands plus the carrier to convey the same information, which isn’t very bandwidth-efficient. Single-sideband transmission trims this down by sending only one sideband, saving power and spectrum.

Independent Side Band takes the idea further by allowing the two sidebands to carry different information streams, effectively multiplexing two channels within the same carrier region. This makes efficient use of spectrum and is useful in military and naval communications where multiple voices or data streams may need to share the same frequency band.

So ISB is categorized under sideband transmission, not encryption, power supplies, or antenna tuning, because its defining feature is how the information is carried in the sidebands of the carrier.