The move to change AM DA proof-of-performance rules has a long, and mostly controversial, history.
In 1989, a group of five consulting engineers proposed radically relaxing the rules so the laborious and expensive field measurements could essentially be eliminated.
But only in the last few years has the broadcast industry come to a consensus on the issue. MM Docket 93-177 was introduced in 1993. A few parties objected and their concerns were addressed in the guidelines proposed by the coalition, according to Benedict.
This rule will not be applicable to all stations. As proposed, “Only arrays consisting of series-fed elements may have their performance verified by computer modeling and sample system verification.” The computer model of the towers must match measured impedance data within fairly restrictive limits. Sample systems must also meet explicit, strict requirements to be eligible. Some arrays with dissimilar towers may also be ineligible, depending upon the sampling situation.
Bravo to the commission if this is really happening. I hear hundreds of AMs are waiting to take advantage of the change to eliminate the expense of pattern tuning, field proofs and monitor point and partial proof maintenance.
