BasicB-003-013-005
Why is FM voice best for local VHF/UHF radio communications?
D
Answer
Basic radio theory
Type
A
The carrier is not detectable
B
Its RF carrier stays on frequency better than the AM modes
C
It is more resistant to distortion caused by reflected signals
D
It provides a good signal-to-noise ratio at low RF signal levels
Answer Notes
Frequency Modulation (FM) is highly preferred for local VHF and UHF communications because it provides exceptional audio clarity and a high signal-to-noise ratio even when the received radio frequency (RF) signal is relatively weak.
Because FM receivers use limiter circuits that strip away amplitude variations, they easily reject static, ignition noise, and other electrical interference that heavily impact Amplitude Modulation (AM) signals. This results in the characteristic 'quiet background' of FM communications.
While other modes like Single Sideband (SSB) are more spectrum-efficient and can cover greater distances, FM delivers superior, broadcast-like audio quality for local, line-of-sight contacts before the signal drops out completely.
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What is the approximate bandwidth of a frequency modulated signal using 5 kHz deviation?