The very high frequency (VHF) radio operates in the 30-300 MHz range. Some models are equipped for digital selective calling (DSC), i.e., sending a narrow-band distress call on a specific frequency at regular intervals. Others are of reduced size for portability.
The VHF radio permits voice communication using distinct frequencies or channels. Portable models are suitable for maintaining contact with ships, tugs or pilot stations.
A VHF radio uses electromagnetic waves for line-of-site communication. Range is limited to the horizon, though certain weather conditions may extend range by bouncing the signal off an atmospheric layer. Increased antenna height also increases range. Certain frequencies in the VHF band are designated as channels used for specific functions (channels 6, 13, 16, 70).
Choice will depend on specific use, portability needs and DSC capability. Frequencies above 100 MHz are well-suited to high-speed data transmission. SOLAS ships in zone A1 are required to have a DSC-capable VHF.
