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FCC Opens NPRM to Allow Computer Modeling for FM Antennas

Four antenna manufacturers and EMF are pushing for the change

fcc new seal logo largeA proposal to allow computational directional FM broadcast antenna pattern modeling in the United States is a step closer to being approved.

The Federal Communications Commission says it believes that the proposed rule change “would provide regulatory parity and ongoing relief for both antenna manufacturers and FM broadcasters while maintaining the integrity of our licensing requirements.”

We had reported earlier that the idea was advancing at the  commission; now the FCC has issued a notice of proposed rulemaking asking for comments.

The commission’s text makes clear that it thinks this is a good idea, but it expressly also asks for help from “engineers, broadcasters, antenna manufacturers, and other interested parties” to help clarify some issues raised by the proposed rule.

The proposal was made in a joint petition from Dielectric, Jampro, Radio Frequency Systems and Shively Labs, all of which make antennas, as well as broadcaster Educational Media Foundation.

Currently, the rules for verifying FM directional patters require physical modeling and measurements.

The FCC noted that verification of directional patterns through use of computer modeling is permitted in both AM radio and TV/DTV and is a familiar concept to the commission and the industry.

It says more than 2,000 full-service FM broadcast stations, which is more than 20% of them, use directional antennas. The change would allow any of those stations that replace existing antennas to avoid the expense of field measurements. It would apply not only to applicants for new FM facilities, but to FM licensees applying for facility modifications.

[Read the full NPRM text.]

The commission also said that given the demand for FM spectrum, “we anticipate an increase in the use of directional antennas. We believe those future broadcast applicants would benefit from this proposal.”

Among questions being asked by the FCC are whether this change could increase the risk of interference to adjacent stations; whether the commission should adopt a particular computer program or underlying model; if not, which computer modeling software programs it should accept for verification; and how FCC staff should confirm the accuracy of such models.

“Perhaps most importantly, we are interested in comments from broadcasters, engineers and manufacturers who have used both computer modeling of FM directional antennas and physical models of the same, and who can discuss their experience regarding the accuracy of computer-modeled antennas vis-à-vis the performance of such antennas as installed.”

Comments in MD Docket 21-422 will be due 30 days after the NPRM is published in the Federal Register, which hasn’t happened yet.