IEEE Std 1260:2018 pdf download.IEEE Guide on the Prediction, Measurement, and Analysis of AM Broadcast Reradiation by Power Lines.
This guide provides a set of procedures that can be used to cope with reradiation ofAM broadcast signals from power lines. It can also be applied to other large metallic structures.
While the procedures listed in this guide may be applicable to reradiation problems from other medium frequency (MF) sources, such as navigation beacons, they are not intended to be applied to reradiation problems from higher frequency sources, such as television broadcast signals. This guide is not designed to be applied as legal evidence of harmful effects of a reradiating structure upon an AM broadcasting station.
In some jurisdictions, the government regulatory or licensing authority has defined specific procedures for the determination of radiation patterns of medium wave antenna systems. Some of these procedures are also contained in international treaties and agreements, and as such are binding on the licensees of the signatory jurisdictions. When there is agreement between the party or parties who are licensed to operate the medium wave antenna system(s) in question and the parties proposing construction of potential reradiating structures, the procedures of the responsible government agency or authority shall have precedence over the method outlined in this guide.
1.2 Purpose
An AM broadcast array is carefully constructed to radiate strongly towards listeners and weakly in directions where interference to other stations could result. Reradiation can occur when the broadcasted signals are parasitically picked up by a large metallic structure and then rcbroadcastcd. or reradiated, from that structure. Many structures may reradiate an AM and other radio signals. e.g., power lines, communications towers, water towers, and buildings.
This can result in a decrease in signal towards listening areas and an increase in signal in protected directions. The process of predicting, measuring, analyzing, and mitigating the interference is complex and nontrivial. and is why this guide was developed. It is anticipated that this guide will be used by owners of potentially reradiating structures and radio stations.
2. Definitions
For the purposes of this document, the following terms and definitions apply. The IEEE Standards Dictionaiy Online should be consulted for terms not defined in this clause.Additionally, IhEE Std 5391 [135] contains definitions related to corona and field effects aspects.
AM broadcast array: One or more towers fed the same broadcast signal but at different current levels and with different delays. By carefully choosing the height, location, current level, and delay for each tower, a far- field pattern can be constructed to broadcast strongly in some directions and weakly in others.
amplitude modulation (AM): Modulation in which the amplitude of a carrier is changed by an amount proportional to the instantaneous value of the modulating wave.
azimuth: The angle between a horizontal reference direction (usually true north) and the horizontal projection of the direction of interest, measured clockwise.
coverage area: The area surrounding the broadcast array that is within the signal strength contour that provides adequate reception.
detuners: Devices attached to a structure that alter the impedance at the connection point such that a minimum of current at the design frequency flows in the structure. They are used to minimize reradiation of the AM signal, thus correcting distortion of the AM station’s antenna pattern. Svn: detuning apparatus; detuning stub; tuning stub.
far-field radiation pattern: Any radiation pattern obtained in the far field of an antenna array.IEEE Std 1260 pdf download.