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Frequency assignments between US and Canadian users are closely coordinated since much of the Canadian population is within VHF radio range of the US border. Certain discrete frequencies are reserved for radio astronomy. The general services in the VHF band are: 30–49.6 MHz: Licensed 2-way land mobile communication, with various sub-bands. [a]
In radio transmission, transmitter power output (TPO) is the actual amount of power (in watts) of radio frequency (RF) energy that a transmitter produces at its output. [1]TPO is a concept related to effective radiated power (ERP), but refers to the power output of a transmitter, without accounting for antenna gain.
The SINCGARS operates on any of 2320 channels between 30 and 88 megahertz (MHz) with a channel separation of 25 kilohertz (kHz). It accepts either digital or analog inputs and superimposes the signal onto a radio frequency (RF) carrier wave. In FH mode, the input changes frequency about 100 times per second over portions of the tactical VHF-FM ...
R/C transmitters may use up to 4 watts on the first five channels and 25 watts on the last, 27.255 MHz. Some in-house paging systems, and car alarms with a paging feature, also use these frequencies, especially 27.255 MHz, where the higher power is permitted. The 27 MHz RCRS channels are not officially numbered by the FCC.
The legally protected range of a station extends beyond this range, out to the point where signal strength is expected to be 1mV/m for most stations in North America, though for class B1 stations it is 0.7mV/m, and as low as 0.5mV/m for full class B stations (the maximum allowed in densely populated areas of both Canada and the U.S.).
For example, an FM radio station which advertises that it has 100,000 watts of power actually has 100,000 watts ERP, and not an actual 100,000-watt transmitter. The transmitter power output (TPO) of such a station typically may be 10,000–20,000 watts, with a gain factor of 5–10× (5–10×, or 7–10 dB).
A standard handheld marine VHF, mandatory on larger seagoing vessels under the GMDSS rules A VHF set and a VHF channel 70 DSC set, the DSC on top A vintage (76–89) marine VHF radiotelephone. Marine VHF radio is a worldwide system of two way radio transceivers on ships and watercraft used for bidirectional voice communication from ship-to-ship ...
The frequency range used by most early radio systems, 25–50 MHz (vhf "low band") is particularly susceptible to the problem of electrical noise. This plus the need for more channels led to the eventual expansion of two-way radio communications into the VHF "high band" (150–174 MHz) and UHF (450–470 MHz).