QUICK AND EFFECTIVE ADJUSTMENT OF STUB DETUNERS BY A 2-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 po wer line must be ''detuned'' to suppress the scattered field. At frequ encies where the power line towers are comparable to a quarter-wavelen gth in height, detuning stubs are usually installed on the power line towers. Each stub must be adjusted to minimize the scattered field fro m its tower. This paper presents a method for Stub adjustment using tw o loop antennas which is quick and simple, and obtains good results in critical situations were more traditional methods were tried and fail ed. The two-loops method is proven in this paper by numerical computat ion. The method was applied ''in the field'' to detune a power line wh ich passes about 900 m from a directional broadcast array. The array's pattern was restored to levels comparable to those before the constru ction of the power line.