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Inverted-L antenna with counterpoise, in a powerful amateur radio station, Colorado, 1920. The counterpoise is the lower grid of horizontal wires, suspended below the antenna. The largest use of counterpoises is in transmitters on the low frequency (LF) and very low frequency (VLF) bands, as they are very sensitive to ground resistance. [2]
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The ground rods create a ground plane under the antenna which increases the gain. The ground rods may extend horizontally from the base, but in antennas fed by coaxial cable as shown here they are usually sloped downward to increase the radiation resistance of the antenna from the 36 ohms of a quarter wave monopole closer to 50 ohms, so the ...
English: Block diagram is from: "Figure 2: Two Channel VHF Base Station," Planning Emergency Medical Communications: Volume 2, Local/Regional Level Planning Guide, (Washington, D.C.: National Highway Traffic Safety Administration, US Department of Transportation, 1995) pp. 42. The word "antenna" was added to the original so that those ...
English: Block diagram is from: "Figure 8: Bandpass Cavity/Isolator Location," Planning Emergency Medical Communications: Volume 2, Local/Regional Level Planning Guide, (Washington, D.C.: National Highway Traffic Safety Administration, US Department of Transportation, 1995) pp. 57.
For monopole antennas operating at lower frequencies, below 20 MHz, the ground plane is usually the Earth; in this case the antenna is a vertical mast mounted on the ground on an insulator to isolate it electrically from the ground. One side of the feedline is connected to the mast and the other to an Earth ground at the base of the antenna. In ...
The base station is one end of a communications link. The other end is a movable vehicle-mounted radio or walkie-talkie. [6] Examples of base station uses in two-way radio include the dispatch of tow trucks and taxicabs. Basic base station elements used in a remote-controlled installation. Selective calling options such as CTCSS are optional.
Used for elevated base station antennas for land mobile radio systems such as police, ambulance, and taxi dispatchers. Mast radiator A radio tower in which the tower structure itself serves as the antenna. Common form of transmitting antenna for AM radio stations and other MF and LF transmitters.