Representatives of most major radio broadcasting groups and the most active AM directional engineering consultants have been working on a proposal to the FCC to finalize a broad revision of the rules that specify how AM stations verify that their directional antennas are working properly.
A recent Radio World Online report details the group’s effort to come to a consensus on the new procedures. The general thrust of the process focuses on how Method of Moments modeling provides a better picture of the actual performance of an antenna system than the conventional field proof measurements, especially in areas of urban clutter. The vision includes a recognition that detuning structures that are a substantial distance from a directional antenna may be counterproductive in providing real interference protection for other stations.
In order to assure that an antenna is performing as intended, the group is working on standards for the antenna monitoring system to allow the greatest flexibility in implementing the antenna sampling system while being absolutely confident that the measurements reflect the actual parameters. A biennial verification procedure is also being proposed.
With the adoption of these changes, AM directional systems will then have a predictable cost of maintenance (barring equipment failures) that make it possible to reasonably budget for the operation of the antenna systems, and avoid the problems in compliance that now occur when a re-radiating structure is built at a distance from the station that “blows out” a monitor point.
The proposed changes will not limit a licensee from using the present procedures where the station is better served by the present “proof of performance” procedures. They are being considered as an optional method of verifying performance.
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