| 1. | Umbrella antennas with heights of 15 to 460 metres are in service.
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| 2. | This type of antenna array is called a trideco or umbrella antenna.
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| 3. | It is also possible to build an umbrella antenna with a grounded tower.
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| 4. | Umbrella antennas can be built as single mast antennas or as multiple mast antennas.
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| 5. | Umbrella antennas radiate omnidirectional radiation pattern.
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| 6. | Thus the umbrella antenna uses the guy wires as the top-load part of the antenna.
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| 7. | The umbrella antenna was used for frequencies around 30 kHz, the ring antenna for frequencies around 20 kHz.
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| 8. | Many smaller anchor blocks providing foundations for smaller towers that supported the umbrella antenna are still visible in the lagoons.
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| 9. | They used grounded or insulated guyed masts with umbrella antennas, or wire-spans across both valleys and fjords.
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| 10. | Two further masts of the station carrying an umbrella antenna are 471 metres tall and the tallest structures in India.
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