Umbrella antenna

Umbrella antenna

An [http://www.j-hawkins.com/nss/goliath.jpgumbrella antenna] is a capacitively loaded electrically lengthened antenna, consisting in most cases of a grounded mast, from whose top wires are affixed, which run to the ground. The end of each wire must be broken by an insulator.

The umbrella name was given because the antenna looks like an umbrella without the cloth. Alternatively, the function of the umbrella wires can be performed in part or in full by guy wires for the central mast, but in most cases (especially for antennas, which are very short in comparison to radiated wavelength) additional umbrella wires are required.

It is also possible to build an umbrella antenna with a grounded tower. Such an antenna requires a separate feeder to the umbrella wires, which are as well insulated against the mast and the ground.

Umbrella antennas are used as single mast antennas for LF and VLF transmission. They were used at most OMEGA Navigation System transmitters and are used at LORAN-C stations with central masts approximately 200 meters tall.


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