Following on the heels of my unimpressive AM HD radio listening test last week, industry stalwart Radio World magazine published a report that comes to terms with the fact that “AM HD radio has stalled.” In fact, I’d say that characterizing AM HD as “stalled” is very optimistic. Instead, reading the same article I come away with the impression that AM HD just barely launched into orbit, and has since fallen.
In terms of statistics, the article notes that there are fewer than a sixth (16%) as many digital AM stations than FM, totaling only about 6% of all AM stations in the US. Furthermore, even amongst the nation’s most powerful big market AM stations that are broadcasting in digital, “most of those transmit their digital signals only during the day.” Tellingly, RW also observes that, “[m]any of the stations on-air with AM HD are owned by members of the HD Digital Radio Alliance.”
The article points to several non-technical factors that might be influencing AM HD’s lack of success. One is the recent FCC decision permitting FM translator repeater stations to be used to rebroadcast AM signals. Another purported cause is the economy (which we can pretty much blame for nearly everything without further explanation). Finally, apparently station groups are waiting for their FM HD signals to start paying off before making further investments on the AM side.
Significantly, it appears that interference issues, including interference with a station’s own primary analog signal, are behind many stations turning off their digital signal. Furthermore, the issue of receivers switching between digital and analog signals when the radio can’t keep locked to the HD data stream is important. On FM the relatively similar fidelity of the analog and digital HD1 channels means that the “blending” between them isn’t particularly noticeable. But on AM the digital and analog programs sound very different, making the blending from one to the other very noticeable and often quite annoying.
Something I didn’t know before is that iBiquity, the owner of the IBOC HD technology, is offering a new “configuration” for AM stations that air mostly talk programming which reduces the digital signal bandwidth in order to reduce interference, heard most prominently on older high performance AM receivers. As a listener, however, I see the bandwidth reduction as a double-edged sword. While it may minimize interference, it also reduces fidelity, which can obviate some of the minimal gains associated with HD technology in the first place.
In a companion piece, Radio World also talked to a number of additional radio engineers not quoted in the first article. While a few, like Clear Channel’s Brett Gilber based in Tulsa, OK, consider the technology a success, others are less sanguine. Harold Beer, who engineers Michigan State University’s WKAR-AM said, “After years of encouraging listeners to get better quality wideband AM radios, we ended up degrading their listening experience with a 5 kHz bandwidth, –35 dB SNR analog signal once we turned on the IBOC digital.”
In the end, whether you read Radio World’s relatively balanced coverage or just listen to AM HD yourself, it’s hard to conclude that this digital medium is anything close to a success. The question is: will the radio industry see fit to throw more cash down the AM HD Radio money pit?
