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Transmission power ranges between 1 and 25 watts, giving a maximum range of up to about 60 nautical miles (111 km) between aerials mounted on tall ships and hills, and 5 nautical miles (9 km; 6 mi) between aerials mounted on small boats at sea level. [7]
A similar broadcast on MF is initially announced on 2182 kHz, with a further frequency specified, e.g., 1770 kHz. VHF optimum range is approximately 30 nautical miles (nmi), effectively line of sight, whereas MF range is much greater at approximately 150 nmi, allowing ships in the Atlantic Ocean and North Sea to receive the broadcast.
The National Distress and Response System (NDRS) was established more than 30 years ago as a VHF-FM-based radio communication system that has a range of up to 20 nautical miles (37 km) along most of the U.S. shoreline.
Very high frequency (VHF) is the ITU designation [1] for the range of radio frequency electromagnetic waves (radio waves) from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter. Frequencies immediately below VHF are denoted high frequency (HF), and the next higher frequencies are known as ultra high frequency ...
The U.S. National Distress System was established in the early 1970s [1] as a VHF-FM-based radio communication system that has a range of up to 20 nautical miles (40 km) along most of the U.S. shoreline for the United States Coast Guard.
Port authorities or other shore-based facilities may be equipped with receivers only, so that they can view the local traffic without the need to transmit their own location. All AIS transceivers equipped traffic can be viewed this way very reliably but is limited to the VHF range, about 10–20 nautical miles.
2182 kHz is analogous to channel 16 on the marine VHF band, but unlike VHF which is limited to ranges of about 20 to 50 nautical miles (40 to 90 km) depending on antenna height, [3] communications on 2182 kHz and nearby frequencies have a reliable range of around 50 to 100 nautical miles (90 to 190 km) during the day and 150 to 300 nautical miles (280 to 560 km) or sometimes more at night.
It is normally positioned 0.5 to 0.8 nautical miles (1 km) before the runway threshold. When the aircraft is above the middle marker, the receiver's amber middle marker light starts blinking, and a repeating pattern of audible morse code-like dot-dashes at a frequency of 1,300 Hz in the headset.