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All-Digital AM Test Data Continues to Look Positive

Smith, Kline call signal characteristics “good” and robust

Results of all-digital AM testing continue to look positive, and NAB Labs is charting a path to eventually asking the FCC for authorization in the event that U.S. broadcasters decide they want to do that.

So said NAB Senior Director of Advanced Engineering David Layer during a Broadcast Engineering Conference session here at the NAB Show in Las Vegas.

The most recent testing involved Greater Media’s WBT(AM), Charlotte, N.C.; Cumulus-owned KTUC(AM), Tuscon, Ariz.; and WD2XXM, an iBiquity test station in Frederick, Md. All of these were already transmitting hybrid digital signals.

NAB Labs is using consumer receivers to characterize the all-digital coverage.

Cumulus SVP Engineering & IT Gary Kline said the all-digital audio sounded “far better than I expected.” He said he walked away from the tests “feeling pretty good about running all-digital HD on AM.”

Greater Media VP of Radio Engineering Milford Smith said the all-digital AM HD Radio signal on the 50 kW clear channel WBT “was very robust.” This was a second round of testing on WBT, to eliminate anomalies found in round one.

The Labs has now conducted drive tests on five AMs and hopes to test on another four facilities in 2014. Cavell and Mertz is developing a lab test facility that eventually will be located at NAB Labs; the point is to develop repeatable tests that back-up the drive data.

Smith told Radio World the NRSC this weekend discussed the possibility of eventually evaluating all-digital AM, similar to tests that members conducted before what was then called IBOC was authorized by the commission.

All HD Radio receivers in the field today can receive an all-digital signal, according to panel participants.