Deep Dive: T8A09
The correct answer is C: Between 10 and 15 kHz. The approximate bandwidth of a VHF repeater FM voice signal is between 10 and 15 kHz. FM requires wider bandwidth than SSB because the frequency deviation (typically ±5 kHz for narrowband FM) plus the audio bandwidth creates a total bandwidth of about 12-15 kHz. For amateur radio operators, understanding FM bandwidth helps explain why FM uses more spectrum than SSB and why fewer FM signals can fit in a given frequency range. The wider bandwidth provides good audio quality and noise immunity.
Why Other Answers Are Wrong
Option A: Incorrect. Less than 500 Hz is way too narrow - that's CW bandwidth. FM needs much more bandwidth for the frequency deviation and audio. Option B: Incorrect. About 150 kHz is far too wide - that's more than 10 times the actual FM bandwidth. FM uses about 12-15 kHz. Option D: Incorrect. Between 50 and 125 kHz is far too wide - that's wideband FM used in broadcasting, not narrowband FM used in amateur repeaters.
Exam Tip
VHF FM repeater = 10-15 kHz bandwidth. Think 'F'M = 'F'requency 'M'odulation = 'F'airly wide (~12-15 kHz). Narrowband FM uses ±5 kHz deviation, creating 10-15 kHz total bandwidth. Much wider than SSB (3 kHz) or CW (150 Hz).
Memory Aid
VHF FM repeater = 10-15 kHz bandwidth. Think 'F'M = 'F'requency 'M'odulation = 'F'airly wide (~12-15 kHz). Narrowband FM with ±5 kHz deviation creates 10-15 kHz total bandwidth.
Real-World Example
Your 2-meter FM repeater signal uses about 12-15 kHz of bandwidth. The ±5 kHz frequency deviation plus the audio frequencies create this bandwidth. This is why FM repeaters need more spacing between channels than SSB - each FM signal needs about 15 kHz, while SSB needs only 3 kHz. The wider bandwidth provides good audio quality and noise immunity.
Source & Coverage
Question Pool: 2022-2026 Question Pool
Subelement: T8A
Reference: 2022-2026 Question Pool · T8 - Signals and emissions
Key Concepts
Verified Content
Question from the official FCC Technician Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the T8A topic.