Subelement N: N – Marine— Topic 85: VHF
Question 3-85N4
Element 3 (GROL)Maximum allowable frequency deviation for VHF marine radios is:
Explanation
VHF marine radios utilize Frequency Modulation (FM) for voice communications. To ensure efficient use of the radio spectrum, prevent interference between adjacent channels, and maintain interoperability, the Federal Communications Commission (FCC) sets specific technical standards for these radios.
Under FCC Part 80 regulations for maritime services, the maximum allowable frequency deviation for VHF marine radios is **+/- 5 kHz**. This standard defines the bandwidth occupied by the signal and is critical for maintaining the 25 kHz channel spacing commonly used in the marine band.
Options like +/- 2.5 kHz represent narrower bandwidths used in other radio services (e.g., some commercial land mobile or amateur radio applications) and would not be compliant for standard VHF marine operation. Deviations of +/- 15 kHz or +/- 25 kHz would exceed the permitted bandwidth, causing significant interference to adjacent channels and violating regulations.
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