VHF Channels and Use
Frequencies within VHF marine band are divided into "channels" for convenience and these channels are further reserved for specific purposes. The chart below summarizes the use for each channel within the VHF marine band:
Follow these rules and protocols when using a VHF marine radio:
- Hail other boaters on channel 16 by stating their name three time, then your vessel name once or twice, then say "over". Example:
- Initial Sender: "Race Committee, Race Committee, Race Committee this is Catalina 32, over"
- Reciever Response: "Catalina 32, this is Race Committee, over"
- Sender Response: "Race Committee switch to 78A, over"
- Receiver Response on Channel 78A: "Catalina 32 this is Race Committee"
- Sender Response on Channel 78A: "bla, bla"
- Keep communications brief using procedure words
VHF, which stands for Very High Frequency, refers to a frequency range used for both marine and aviation radio traffic, among others. VHF radio encompasses the frequency range from 30 to 300 megahertz with 118 to 137 megahertz reserved for civil aviation and 156 to 162.025 megahertz reserved for marine use.
UHF, or Ultra High Frequency, is the more common standard frequency range used for radio traffic on land. UHF represents the frequency range between 300 megahertz and 3 gigahertz.
UHF radio waves are capable of penetrating buildings and other obstacles, while carrying considerable data. By contrast, VHF radio waves, with longer wavelenghts, are stictly line of sight but are capable of traveling over twice the distance of UHF. For this reason, VHF is the preferred frequency range for communications over open water and air.
Antenna Height, Signal Strength, and Distance
Since VHF is a limited to line-of-sight applications, the curvature of the Earth is a limiting factor on VHF signal propagation. For a man standing on level ground at sea level, the horizon is approximately 3 statute miles away. For this reason, the signal range for most handheld VHF radios broadcasting with a transmission power of between 3-6 watts, is typically quoted in the 5 mile range.
However, if the VHF radio antenna is placed at the top of a sailboat's mast, the line-of-sight distance to the hoizon can be increased to over 20 miles. When a sailboat is equipped with a fixed mount VHF radio broadcasting with 25 watts, the effective range of the transmission can exceed 20 miles. Fixed mount VHF radios offer greater transmission power than handheld units (25 watts versus 3-6 watts), but the biggest factor in signal propagation is the height of the antenna.