Quick and effective adjustment of stub detuners by a two-loops method

When reradiation of an AM broadcast station´s signal from a power line leads to a violation of the station´s regulatory requirements, the power line must be “detuned” to suppress the scattered field. At frequencies where the power line towers are comparable to a quarter-wavelength in height, detuning stubs are usually installed on the power line towers. Each stub must be adjusted to minimize the scattered field from its tower. This paper presents a method for stub adjustment using two loop antennas which is quick and simple, and obtains good results in critical situations were more traditional methods were tried and failed. The two-loops method is proven in this paper by numerical computation. The method was applied “in the field” to detune a power line which passes about 900 m from a directional broadcast array. The array´s pattern was restored to levels comparable to those before the construction of the power line