Technician 2026-2030T8A09

What is the approximate bandwidth of an FM voice signal on VHF repeaters?

C
Answer
Signals, emissions, and modulation
Type
A
Less than 500 Hz
B
About 150 kHz
C
Between 10 and 15 kHz
D
Between 50 and 125 kHz

Answer Notes

Frequency Modulation (FM) bandwidth is determined by a combination of the transmitter's frequency deviation and the highest modulating audio frequency, often calculated using Carson's Rule. For standard VHF repeater operations, amateurs typically use a 5 kHz deviation with a maximum audio frequency of about 3 kHz. This combination results in an overall bandwidth footprint of roughly 10 to 15 kHz. While FM takes up considerably more spectrum than a 3 kHz SSB signal, it trades this wider bandwidth for much better audio quality and a high resistance to static. Commercial FM broadcast stations use a much wider bandwidth of about 150 kHz for high-fidelity stereo music, which is why that distractor is incorrect for amateur voice repeaters.
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What is the approximate bandwidth of a typical single sideband (SSB) voice signal?
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What is the approximate bandwidth of AM fast-scan TV transmissions?