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Land mobile radio systems use channels in the VHF or UHF bands, since the antennas used at these short wavelengths are small enough to mount on vehicles or handheld transceivers. Transmitter power is usually limited to a few watts, to provide a reliable working range on the order of 3 to 20 miles (4.8 to 32 km) depending on terrain.
The VHF band is the first band at which efficient transmitting antennas are small enough that they can be mounted on vehicles and portable devices, so the band is used for two-way land mobile radio systems, such as walkie-talkies, and two way radio communication with aircraft and ships (marine radio).
A directive antenna with moderate gain of about 8 dBi often used at UHF frequencies. Consists of a dipole mounted in front of two reflective metal screens joined at an angle, usually 90°. Used as a rooftop UHF television antenna and for point-to-point data links. Parabolic The most widely used high gain antenna at microwave frequencies and above.
Their compact size makes helicals useful as antennas for mobile and portable communications equipment on the HF, VHF, and UHF bands. [citation needed] A common form of normal-mode helical antenna is the "rubber ducky antenna" used in portable radios. A handheld two-way radio, with the rubber sleeve removed from the antenna.
Antennas which have these inductors built into their bases are called base-loaded whips. The rubber ducky is an electrically short quarter-wave antenna in which the inductor, instead of being in the base, is built into the antenna itself. The antenna is made of a narrow helix of wire like a spring, which functions as the needed inductor. The ...
The advantages of /P operation include the use of large empty spaces where full size beam and wire antennas can be erected on tall trailer mounted masts. If operating on VHF/UHF, this can mean a location on the top of a hill or cliff, with clear line of sight to the horizon. The main disadvantage is normally the power supply available.