FCC Set to Allow Directional FM Antenna Computer Modeling

ByErma F. Brown

May 8, 2022 , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,


Utilizing the technology will save broadcasters money

The FCC appears to be moving quickly toward allowing FM broadcasters in the United States to use computer modeling software for their directional antennas.

A new draft order has come forward just six months after the commission released a notice of proposed rulemaking based on a petition from antenna manufacturers Dielectric, Jampro Antennas, Radio Frequency Systems and Shively Labs. The manufacturers want the FCC to allow FM broadcasters the option of submitting computer models to reduce costs of tower projects without jeopardizing technical standards.

The draft order will be considered for adoption at the FCC monthly meeting on May 19.

When seeking a license, FM radio stations using directional antennas currently are required to provide physical measurements to verify their directional pattern. To do this, stations or their representatives must build a full-size mockup of the antenna or a scale model. That type of work typically is done by the antenna manufacturer.

The draft order would give applicants the option of submitting computer-generated proofs of FM directional antenna patterns from the manufacturer, in lieu of measured pattern plots and tabulations.

Detailed information on who performed the computer modeling would need to be provided, the FCC says.

In addition, the rules would require “a description of the computer modeling software used and the procedures applied in using the software, including a description of all radiating structures included in the model,” according to the draft proposal.

Also, the commission is poised to require that the first time the directional pattern of a particular model of antenna is verified using computer results, the FM station will need to submit the results of the computer modeling and measurements of either a full-size or scale model of the antenna; again this would likely be done in concert with the manufacturer.

The FCC says the requirement “is in order to demonstrate reasonable correlation between the measurements achieved and the computer model results.”

It continues: “Once a particular antenna model or series of elements has been verified by any license applicant, subsequent license applicants using the same antenna model number or elements and the same modeling software may cross-reference the original submission by providing the application file number,” the FCC concluded.

The commission appears to have decided not to expand the range of entities authorized to perform computer modeling beyond manufacturers.

Referring to input it received in its NPRM, it wrote: “Although commenters largely agree that license applicants should be able to rely on manufacturer computer modeling to verify FM directional patterns for that manufacturer’s antennas, there was less agreement as to whether others should be allowed to perform computer modeling to verify FM directional antenna patterns.”

Chairwoman Jessica Rosenworcel in her preview of this month’s meeting says the draft order would “decrease regulatory costs and bring our FM regulations in line with other broadcast services.”

The commission calls the revision a “modest rule change” that allows for similar treatment of FM and LPFM directional antenna performance verification to that used for AM and DTV licensing.

The most common reason for a commercial full-power FM to use a directional antenna is to allow it to “short-space” to another FM station while maintaining contour protection to that station, according to the FCC. There are about 900 directional FM stations licensed in the U.S., according to the commission.

The National Association of Broadcasters was mostly on board with the initial FCC proposal to allow directional FMs reliance on computer modeling and move away from required real-world testing, calling computational modeling of FM directional arrays “already mature and capable of producing comparable accuracy to physical measurements.” However, antenna manufacturer Electronics Research Inc. has expressed concerns about the proposed change.

[Related: “NAB Sees Benefits of FM Directional Antenna Modeling”]



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