On October 29, 2009, the Mass Media Bureau released a Public Notice that provides clarification of the Commission's amended rules allowing computer modeling techniques to verify that AM directional antennas perform as authorized. The Notice does not establish binding precedent, but merely provides general guidance in light of the numerous questions the Media Bureau received regarding the new procedures for computer modeling techniques, also known as "moment method modeling." The Bureau's guidance included, in part, the following points:

  1. Use of moment method modeling is only permitted for directional antenna towers consisting of series-fed radiators with standard ground systems. Folded unipoles and sectionalized antennas are not eligible for the new proof techniques.
  2. A post-construction surveyor's certification is required to verify that directional array towers have the proper spacing and orientation. A tolerance of 1.5 electrical degrees for the location of each tower in a directional array is allowed. Licensed stations applying to be relicensed under the new rules will be exempt from the surveyor's certification requirement, as long as there is no change in the authorized theoretical pattern or patterns. The variation of the physical dimensions used in the model must be between 75 and 125 percent of the tower length represented.
  3. Moment method proofs must contain a statement of calibration verifying that the antenna monitor is calibrated according to manufacturer's specifications
  4. Directional AM stations may choose to file a moment method proof to cover new facilities with a construction permit or to support a new license without monitoring points. Commercial licensees must pay both the new license fee and the directional antenna fee because the same scope of work is required for a moment method proof, regardless of which situation the proof covers. Stations filing a moment method proof for either purpose should indicate on Section III of Form 302-AM that the purpose of the application is "Station License," and, if possible, indicate somewhere on the form that a moment method proof is being submitted.
  5. A licensee that would like to convert to operation authorized by a moment method proof must first request and receive Special Temporary Authority to operate with antenna monitor parameters determined by the moment method before readjusting the array to the new parameters.

A copy of the Public Notice is available here.