Question T8A09
From subelement T8 - T8A
What is the approximate bandwidth of a VHF repeater FM voice signal?
Why is this correct?
VHF repeater FM voice signals occupy between 10-15 kHz bandwidth. This is significantly wider than SSB voice (3 kHz) or CW (150 Hz) because FM modulation requires more frequency space to encode voice information. Option A (500 Hz) is too narrow for voice, Option B (150 kHz) exceeds typical amateur allocations, and Option D (50-125 kHz) is unnecessarily wide for voice communications.
Memory tip
Remember the bandwidth hierarchy: CW is narrowest, then SSB voice, then FM voice. FM needs roughly 3-5 times more bandwidth than SSB because it encodes information differently. This pattern helps across all modulation comparison questions.
Learn more
VHF/UHF FM repeaters use this bandwidth to provide clear, full-fidelity voice communications within their coverage areas. The 10-15 kHz allocation represents a balance between audio quality and efficient spectrum usage. Part 97 emission standards ensure repeaters don't exceed necessary bandwidth while maintaining adequate signal-to-noise ratio for reliable regional communications. Modern narrow-band FM systems can operate in as little as 5 kHz while maintaining acceptable audio quality.
Think about it
Why do you think FM voice requires significantly more bandwidth than SSB voice, yet both can carry the same audio information effectively?