AM Protection for Powerlines & Watertanks

Construction cranes may distrubt AM station coverageMany other types of permanent and temporary structures can cause problems for AM broadcast stations. These disruptions of the AM station’s operations can cause loss of coverage, off-air time, and interference to other stations. In addition to causing federal regulatory violations, significant economic damages to the AM station may ensue.

In addition to pattern disruption, these structures can cause non-ionizing radiation (RF) safety issues to arise. These issues should be thoroughly investigated as well.

Typical structures that cause problems for AM station operations are steel transmission towers, water tanks, derricks, smokestacks, large buildings and bridges. Structures beyond two miles from the AM station are normally of little concern. Impact within that area must be evaluated based on specifics of the AM station operation and the physical and electrical characteristics of the new structure. It is very important that an engineering study be made before commencing site work. This may include preconstruction measurements to document baseline AM performance to protect the constructor from later claims of harm.

Use the Free LBA AM Protection tool to see if your construction is in a zone with AM interaction hazard concerns. Its easy - just input your construction site coordinates.

The FCC has a long established principle that AM licensees have to be protected from the effects of new nearby reradiating structures. In a recent Public Notice on this issue, the FCC reminded others of their responsibility to protect existing AM licensees:

Water tanks may disrupt AM station coverage“The (FCC) has received a number of complaints from AM Broadcasters concerning the construction … near their AM facilities … The Commission’s policy is clear. Whether by imposition of specific conditions or by the operation of law, (the builder) of a new facility is obligated to take all the necessary steps, including the financial burden, to correct interference problems caused by the new … construction.”

“The (builder) shall be responsible for the installation and continued maintenance of detuning apparatus…”

Power line transmission towers may affect AM tower stationsFurthermore, it also set out a number of formal steps required to demonstrate that AM station protection has been achieved, as well as interim operational requirements which must be coordinated with the AM station. While this specific notice is directed to common carrier licensees, in other similar notices and judicial actions the FCC consistently has held that this protection requirement is universally applicable on behalf of its licensees.

Because of the possible economic harm to the AM, there may also be other significant legal and financial exposure for a builder not choosing to protect the AM station.

The significance of these impacts may be seen in the following examples: In a Florida situation, an AM station is in the process of suing several licensees and a non-licensee structure owner to compel them to pay large amounts of money to correct its AM transmission pattern that has been altered due to a deficient detuning system. In Texas, a power company redesigned over two miles of new high voltage transmission line to avoid impacting an AM station. In New England, a city was required to give land to, and pay to relocate (at the cost of several hundred thousand dollars), a directional AM affected by their construction of a new power plant.

LBA can evaluate your exposure for both AM Pattern Protection (PPT) and RF Safety and recommend appropriate remediation, or no action, as the case may be. Our experience includes remediation of hundreds of AM protection incidents. LBA does not work for the AM station. We are soley on your side! Remember, always test your construction site coordinates with the LBA ToolBox. If an AM Protection incident is identified, contact the AM experts at LBA for immediate, objective guidance.


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Greenville, NC 27834


About LBA

LBA Group companies serve technical infrastructure needs related to the broadcast, wireless, electromagnetic compatibility and safety sectors worldwide. We provide consulting, training and other telecommunications industry services. We also produce and market hardware for radio transmission, RF shielding, safety and testing.