Glen Clark: Let AMs Go IBOC At Night

Communications consulting engineer Glen Clark, president of Glen Clark & Associates, has petitioned the FCC to reconsider its ban on AM stations using IBOC at night. The interference concerns that led to the ban can be addressed in ways that would allow the “majority” of 24-hour AMs to go IBOC immediately, states Clark in a Petition for Reconsideration filed at the FCC.
It is true, he states, that “a minority” of AMs would cause “significant interference” to their neighbors if they went digital at night, however he believes the number is “small”.
The FCC already has a spectrum allocation guideline, the desired-to-undesired ratio, that can predict which AMs would likely cause interference to their neighbors with nighttime IBOC operation, so its unnecessary to ban all AM nighttime IBOC operation, he states. FCC rules require co-channel stations to have a D/U ratio of 20-to-1, meaning any interfering signal can be no stronger than 1/20th of the strength of the desired signal. First adjacent channel stations are required to have a D/U ratio of 2-to-1 or more at the periphery of the primary service area. These rules, he states, do not change from day to night.
Expanded band stations are subject to a more stringent nighttime allocation standards, a 2-to-1 D/U ratio for first-adjacents. He proposes authorizing all expanded band AMs for nighttime IBOC operation immediately.
He proposes the commission can identify AMs that could go IBOC at night with no significant additional 1st adjacent channel interference by asking: “What stations could satisfy the same standards at night as are implied to be adequate by the commission’s approval of IBOC during daytime hours?” Or, “What stations could satisfy the current standards in Part 73.182 with reference to first-adjacent channel stations without drawing upon grandfathered radiation rights?”
He’s suggested a five-rule test to quickly assess which stations should go IBOC at night and plans to discuss his theory at the IBOC presentations on Sunday, April 6 at NAB2003.