The author is owner of Remote Possibilities, a broadcast and remote production services provider.
With due respect to Larry Langford I take issue with his call to dispense with annual AM NRSC proofs. Mr. Langford brings up the positive side of features and reliability of modern audio processors and transmitters to support his case. True, but I do not want to risk my professional reputation on a bet that modern AM transmission systems will never fail in ways that can cause harmful interference.
The Federal Communications Commission appears to have lost sight of its original purpose to regulate stations in order to mitigate interference. Connections corrode, water gets into places where it causes problems, and age, heat and dirt take their toll — even in the most reliable of transmission systems. An annual spectral checkup was and continues to be a prudent practice.
We tell nontechies that we use test equipment because the five human senses do not tell us what we need to know about equipment health. We should not use any type of sixth sense to predict the future and tell the commission that annual measurements are no longer needed. Experience tells us that, to quote the oft-quoted Mr. Murphy, “If anything can go wrong, it will go wrong.” Our experience tells us that that guy named Murphy presides over the future whether we like it or not.
Now that doing away with AM NRSC measurements is on the table, I submit there is a case for requiring annual testing for FM band occupied bandwidth and spur measurements. The VHF aeronautical radio band starts just above the top of the FM band. Both the FCC and the FAA take a dim view of FM broadcast spurs popping up in the middle of air-to-air or air-to-ground aircraft communications. This is why FM licensees should be required to check transmitters periodically, not just when they go into service.
The FM interference risk is not just for simple sum and difference products in the VHF range. Cabinet leakage has been found in at least one currently marketed transmitter model causing out of band emissions out to the seventh harmonic. This and other problems can cause interference to other services including the cellular bands.
Those of us who do annual NRSC measurements or contract with engineers who have the proper equipment to accurately perform the requisite measurements need this annual requirement. We have to use this and the dwindling number of FCC technical rules to help assure licensees that they are less likely to get a Notice of Apparent Liability citing interference. Absent an FCC rule, annual occupied bandwidth and spur measurements will go the way of other rules that are no longer enforced. Loss of FCC technical rules helps many licensees justify not have their equipment tested once a year. Let’s advise the commission to leave annual occupied bandwidth and spur measurements in place to help us continue to protect our employers’ most valuable asset — their licenses!
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