By Harry Cole
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The FCC has requested comments on a proposal to let some, but not necessarily all, AM directional applicants use moment method computer modeling to demonstrate that their directional antennas perform as authorized.

The proposal was advanced by a coalition of broadcast engineering mavens – broadcasters, manufacturers, consulting engineers – a couple of weeks ago, following several months of meetings and deliberations.  The idea is to reduce the burden, both on AM applicants and on the Commission’s processing staff, by eliminating the need to conduct and analyze field strength measurements of directional arrays in order to verify that they’re working like they’re supposed to.

Historically, the Commission has required directional AM applicants to undertake elaborate, labor-intensive measurements to confirm that their arrays were working properly.  Those measurements were then sent to the Commission, where staff members reviewed them as well.

But moment method computer programs (also referred to as NEC, or Numerical Electromagnetics Code, programs) permit the accurate calculation of actual performance based on certain internal antenna parameters, such as current and phase.  The coalition also came up with draft rules which would permit the use of moment method modeling to assess the effect of nearby reradiators on the resulting pattern.

The coalition’s proposal, which is supported by 20 group owners and 10 consulting firms, has been submitted to the Commission in connection with its long-running inquiry in AM directional antennas (MM Docket No. 93-177).  While not all AM applicants would be eligible to use the proposed modeling approach, it appears that that approach would still save considerable time and effort throughout the industry.

Comments on the coalition’s proposal are due by July 23, 2007; reply comments are due by August 22, 2007.