On August 14, 2013 the Federal Communications Commission adopted a report that looked into “an inquiry into the Commission’s policies and rules regarding AM radio service directional antenna performance verification.” This reported was aimed at clarifying the rules concerning the construction of cell towers near AM towers.
“In AM radio, the tower itself functions as the antenna. Consequently, a nearby tower may become an unintended part of the AM antenna system, reradiating the AM signal and distorting the authorized AM radiation pattern. Our rules contain several sections concerning tower construction near AM antennas that are intended to protect AM stations from the effects of such tower construction,” the FCC’s ThirdReport and Order explained.
Even though the Commission has a “newcomer” policy that stipulates a new party constructing or modifying a facility is responsible, financially or otherwise, to eliminate objectionable interference to existing stations, there were no explicit rules. Without precise rules to follow, there was confusion among tower owners with respect to the proper procedures to protect nearby AM stations.
The new rule proposed to replace the previous approach with one that, “defines the critical distance from both non-directional (single antenna) and directional (multiple antennas) AM stations based on the pertinent AM station’s frequency and the proponent’s tower height. The proposed rules would require a party proposing to construct a new tower or significantly modify an existing tower within the pertinent critical distance to provide notice to the AM station at least 30 days prior to the planned commencement of construction. Such party would be responsible for the installation and maintenance of any detuning apparatus necessary to restore the AM station’s radiation pattern. The proposed rules would designate moment method modeling as the principal means of determining whether a nearby tower affects an AM pattern,” the FCC explained.
Shorter towers will not be affected by these changes. “Similarly, the proposed rules excluded all antenna structures mounted on buildings from AM proximity analysis,” the FCC reported. While these new rules affect prospective towers, if there are AM towers that have been negatively affected by towers previously constructed then they can show the commission the adverse impact within one year of the effective date of the new rules (August 14, 2013). Then the commission can direct the tower owner to install and maintain any additions that are necessary to restore the proper operation of the AM station.
“A one-year time frame will allow a potentially affected AM station sufficient time to identify the source of the pattern disruption and prepare and submit an adverse impact showing. We authorize the Commission staff, if necessary, to direct the tower owner to take appropriate ameliorative action to correct disturbances to the radiation pattern of an AM station caused by the tower construction or modification, such as installing, maintaining, and, if necessary, adjusting any detuning apparatus necessary to restore proper operation of the AM antenna,” according to the FCC.