The Corporation for Public Broadcasting announced recently that it has provided $7.74 million in grants to assist 85 public radio stations in their transition to digital operations. This announcement is interesting, coming as it does only a week after Communications Daily reported on August 16 that CPB engineers were finding that HD Radio was providing the coverage that was initially expected. The press report indicated that CPB was discovering that HD Radio was providing coverage to only about 60% of a typical FM station’s analog service area, and that it was causing more interference issues than had been expected. CPB was planning additional studies to look into these issues.
In discussing HD Radio implementation issues with broadcasters over the last few months, I’ve heard similar reports about coverage. I’ve also heard troubling reports of interference to adjacent channel FM stations from HD operations – especially from multicast operations. The interference is usually caused to weaker FM stations. These were stations had listenable signals in a market that were no longer listenable in some areas after a station on an adjacent channel began digital operations (and it has not just been on first adjacent channels). While these problems can apparently be addressed by the use of filters by the digital station, the levels of interference are often below the FCC prohibited levels of out-of-band emissions, so cases have arisen where there have been disputes about the resolution of these problems. Of course, as the stations experiencing the interference had weak signals to begin with, the problem could be caused by issues other than the new digital operations. It will be interesting to see if CPB confirms that these alleged cases of digital interference were in fact caused by the new digital radio operations. And it will also be interesting to see if the FCC’s digital radio order, when it is finally released (see our July 17 posting on the expected release of the FCC order on "final" digital radio rules), provides any process for addressing any such complaints of interference.