All-Digital AM Tests on the Table

Members of the NAB Radio Engineering Committee are pondering testing iBiquity Digital’s all-digital AM system.


The idea is one of several that has been bandied about, I hear, as part of the overarching goal of helping medium- and small-market AMs without a powerful signal to remain economically viable.

Beasley has committed to finding a station to test on and at least two other broadcast groups have as well, Beasley Vice President of Engineering/CTO Mike Cooney tells me.


The key is finding an underperforming station and turning off the analog temporarily in order to test the all-digital system, both day and night.   


Years ago, I remember iBiquity conducted tests of its AM all-digital technology and anecdotally reported an increase in coverage. But that was with the HD gear of several generations ago. It would be interesting to see all-digital AM performance with the HD Radio gear of today.


IBiquity has also said for years that the interference issues inherent with the AM band could potentially be improved with an all-digital system.


Other potential upsides? With all-digital “your bandwidth goes from 30 kHz back town to 20 kHz,” said Cooney, who adds an all-digital AM system also requires less transmission power.


Granted, some AMs may need equipment upgrades to make an all-digital chain work, however, knowing what you’d need would help you plan, I think.


Beasley is especially interested in results, having previously turned off the digital on several of its AMs due to interference concerns, we’ve reported.


The idea of the testing is to get some real-world data over a sustained period of time and quantify the results. “We would do before-and-after signal measurements to compare analog and digital coverage differences,” he tells me. Testing would also determine whether an all-digital signal caused any first-adjacent interference, or improved existing interference.


Drive tests would be conducted in rural and city areas in several markets.


Committee members still need to identify test stations.


The idea of testing the all-digital system is intriguing as struggling AM owners try different things to keep their stations relevant as consumers increasingly turn their attention to FM and online options. While big-market AM powerhouses remain profitable, the economic picture is not so rosy for other AMs, some of which have increasingly turned to rebroadcasting their signal on FM translators.


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