MW antenna "Vigra" (Norway), guy coil
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All photos by Jan Inge Ramsvik
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guy coil
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The use of guy coils
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The electrostatic field during thunder storms which is homogeneous when no conducting elements are present, could lead to field strengths greater than 10 kV/m. In the vicinity of the mast the field strength is very inhomogeneous with high field strength close to the mast.
A flash over an insulator, which is caused by high differencesof electrostatic potentials along the guy may result in a lasting arc, which is fed by the RF energy of the transmitter. This effect can be avoided by grounding the guy ropes electrostatically. Only two insulators, one at the top close to the mast, and one at the bottom close to the guy foundation are used.
The lower insulator is bridged by a coil, which grounds the guy statically.
These coils are tuned to values, which reduce the current on the guys having practically no influence on the total current distribution of the antenna.
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