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A year ago, the FCC approved the use of a computer modeling technique, known as "moment method modeling", to allow certain AM stations to do Proofs of Performance of directional antenna patterns without the costly and time-consuming process of proofing the antenna performance through the use of actual field strength measurements.  Last week, the FCC issued a Public Notice clarifying the process for the use of this process.  The Commission notes that these guidelines are issued based on the staff's current interpretation of the rules, that the notice is not intended to be precedential and to bind the Commission, and that these issues will be addressed by the staff in more detail as specific cases arise.    

The Public Notice addresses subject such as:

• Types of Antenna Systems Eligible:  Only antennas with series-fed radiators can use this method - not those with folded unipoles or sectionalized antennas
• Tower Location Tolerance: Noting that the a surveyor must certify that the antenna has been properly located and each tower is properly oriented, with a tolerance of 1.5 electrical degrees for each tower in the array
• Antenna Monitor Calibration:  Reliance on the technique requires a certification that the antenna monitor has been properly calibrated in accordance with manufacturer's specifications
• Filing Fees:  Applicants must pay the license fee and directional antenna fee for both licenses to cover construction permits or to support a new license without monitoring points.
• Specific information for accounting for base region effects when base sampling is used, agreement between calculated and measured tower base impedances, the requirement to measure impedance of sampling line with sampling device connected, and the determination of licensed parameters vs. operating tolerances is also provided

More specific information can be found in the Commission's Public Notice. 

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In a recent decision, the FCC adopted new rules for AM station proofs of performance that make the process much simpler.  We wrote about this proposal when it was advanced, here.  The order adopted a week ago allows stations installing new series fed AM directional antennas to avoid the time-consuming and expensive process of doing a full proof of performance, by instead using a computer modeling process plus a limited number of actual measurements.  Comments filed in the proceeding convinced the FCC that this process would be as accurate as the full proofs that had previously been required for new AM stations and for many changes to existing stations.  Providing this option to AM broadcasters should greatly simplify and expedite the process of completing AM construction and the licensing of such stations.

As part of this order, the FCC also asked for further comments to discuss whether the construction of communications towers - even those that do not otherwise fall under FCC jurisdiction because, for instance, they are too short to require tower registration which is primarily triggered by FAA considerations - near to AM directional towers should also be required to use this same computer methodology to determine the effect that new construction would have on the nearby AM station.  If so, would parties proposing such new construction have to notify nearby AM stations, or just some subset of AM operators (such as those that are themselves operating under program tests).  If notification is to be required, how much advance notification should be required?  Comments on this proposal are due 30 days after this order is published in the Federal Register. 

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The FCC has asked for public comment on a change in its rules which would allow broadcasters to conduct proofs of performance for a new directional AM antenna system to be conducted by a computer modeling system, rather than the extensive system of field tests that currently are required. While generations of broadcast engineers have grown up slogging through swamps, driving through fields and even flying in helicopters to conduct field strength readings to prove that AM antenna systems are operating in compliance with the parameters specified in their applications as submitted to the FCC, this proposed new system would allow all this to be done by computer in most instances. Comments on the proposals can be filed with the FCC on or before July 23, with replies due on August 22.

This proposal was filed at the Commission by a consortium of broadcasters, broadcast engineers and antenna manufacturers who had concluded that the existing process was overly expensive and cumbersome and similar results could be achieved by current computer technology.  Whether the FCC concludes that this is in fact the case will depend on the comments filed in response to this notice. 

As these comments are requested to refresh and update the record in an existing rulemaking proceeding to assess the performance of AM directional antenna systems – a proceeding which was actually initiated by a Petition for Rulemaking filed in 1989 – the FCC could immediately issue new rules following the results of this inquiry. Thus, relief for AM broadcasters, making the process of building AM directional antenna systems much faster and cheaper, may be on the way in the short term.

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