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Citadel Re-evaluates AM HD-R Nighttime

Citadel Broadcasting halted AM nighttime IBOC operations in early October after receiving interference complaints.

Citadel Broadcasting halted AM nighttime IBOC operations in early October after receiving interference complaints.

Citadel Director of Corporate Engineering Martin Stabbert said his company is taking a step back and evaluating the situation. The company’s 10 AMs stopped nighttime HD-R operations as of Oct. 1. They are still broadcasting in HD-R during the day. Overall, 16 of Citadel’s 66 AMs have converted and four more were in-process earlier in the month.

An excerpt from his memo to staff reads: “… In response to the lackluster performance, the limited benefit, and various reports of significant interference, Citadel is suspending nighttime AM HD operations at this time. Please reinstate your previous procedures for daytime-only HD operation as soon as possible. …”

The company received interference complaints from listeners and stations on adjacent channels, the latter from both Citadel- and non-Citadel-owned stations in and outside the markets.

Most of the complaints center around 50 kW Class As, Stabbert said, although internally, Citadel has also observed effects from lower-powered stations on adjacents at night.

Stabbert stressed that Citadel’s action is not a criticism of Ibiquity nor of its technology. The move, however, comes at a time when the impact of AM digital at night, which only recently was OK’ed by the FCC, is being closely scrutinized by those who believe it could fundamentally damage the band.

With this action, Citadel, a member of the HD Digital Radio Alliance, offered itself as a testbed to Ibiquity for itself and other radio groups.

Of the issue overall, Stabbert said, “It’s an unknown, and that’s why we’re stepping back to work with Ibiquity to make it a known. I can only see that good will come from our stance of stepping back to evaluate performance.”

Ibiquity Digital said it has received few complaints about interference and that the “vast majority” of feedback it’s received about AM nighttime has been positive.

“We understand Citadel’s caution and are working with them to understand what they are experiencing and to address their concerns,” said a spokeswoman.

It took some time to get feedback after the stations began running 24/7 in HD-R. “I would imagine some people listening the first couple of nights wondered what was going on but didn’t call the station, especially since the [nighttime] launch was over a weekend,” said Stabbert.

Some stations had no complaints, he said, and roughly the same number did.

Listeners who have complained say they hear hiss and adjacent-channel stations say they hear noise on the channel, he said, adding that most of the impacted adjacents are stations Citadel owns.

After ‘Stepping Back,’ What’s Next?

Citadel and Ibiquity were figuring out the next steps — and who would pay for what — earlier in the month.

Stabbert said Citadel employees have been measuring the effects of AM nighttime IBOC subjectively — by ear — so far; it’s working with Ibiquity to determine what equipment and resources are needed to devise a resolution.

That may involve some on/off testing and/or reducing the injection of the digital energy into one or both sidebands.

“We have a general idea of what’s going on; as we step back, we can do empirical testing with Ibiquity,” Stabbert told Radio World.

He couldn’t guess how long the process would take, noting “The sooner we step back and evaluate the next move, the sooner we can make that move. If there is a problem, we want to help Ibiquity tweak it so that it’s less of an issue, or a non-issue.”

Write to Radio World about your experiences with AM digital. E-mail [email protected].