What is the purpose of guard bands in frequency planning?

• A. To allow for future expansion in the same channel
• B. To prevent adjacent-channel interference and ensure compliance with spectrum regulations
• C. To reduce transmitter power requirements
• D. To increase total usable bandwidth

Answer: (B)

Guard bands provide spectral separation between channels to keep signals from one channel from spilling into the next. This spacing accounts for non-ideal transmitter and receiver filters, out-of-band emissions, and frequency drift, so the system stays within regulatory emission masks. By design, guard bands prevent adjacent-channel interference and ensure compliance with spectrum regulations. They don’t enable future expansion within the same channel, they don’t reduce transmitter power, and they slightly reduce usable bandwidth to protect neighboring channels.