The rules for determining when construction of a new tower may cause a distortion of the pattern of a nearby AM station, and when the party building the new tower has a financial obligation to remedy any interference caused, were clarified by the Commission in an order released late last week. The order makes clear that all towers used by FCC licensees must abide by these rules, putting into formal rules the existing general obligation that all “newcomers” that create interference to an existing licensee must be responsible for rectifying that interference. There was apparently some question about the duty of newcomers to rectify issues that they cause to AM stations, as the rules for all non-broadcast services did not explicitly include language embodying that concept.

The Commission also made clear that the distortion of an AM stations pattern would be measured by the “moment method,” a computer program that will determine if there is a disruption to the pattern, rather than by actual field strength measurements. Doing a “proof of performance” of an AM station can be a long and costly process. Thus the FCC several years ago authorized the moment method of modeling AM patterns (see our article here). In this order, the Commission extends the reliance on this method to the resolution of complaints about new tower construction interfering with existing AM patterns. Other specifics of the order are set forth below.Continue Reading FCC Sets New Rules for Determining When New Tower Construction Triggers Financial Responsibility for Disrupting AM Station Antenna Patterns