HD Radio: Deficiencies

Bob Struble Mr. Junk
"An Interview With: Robert J. Struble"

"How was iBiquity launched? It started out essentially as a science project formed by some radio groups back in the early 90s... The core staffing of the business came out of Westinghouse’s defense business which was based in Linthicum, Md. We took some world class engineers from the defense business and formed the company... Back then to call it a science project would have been an insult to scientists... We’re making this stuff up as we go along, which is exciting."

"A Smart Choice Of HD-2 Formats"

"One of HD-2's challenges seems just to be staying on the air. At DCRTV.com, Dave Hughes gave Clear Channel's eRockster (now heard on WWDC's multicast channel) a plug only to note the next day (July 12) that it was off the air, as was WTOP's HD-3 traffic/weather channel. That's an experience I've had with many of New York's HD-2 channels as well, by the way. What's even more pathetic about the 'here-one-day-and-gone-the-next' status of local HD Radio channels is that I'm probably the only one who's noticing the absences, Hughes writes."

"DaySequerra Targets HD Radio Time Alignment Drift"

"President David Day in the announcement described the product as a solution to one of the most nagging problems facing HD Radio station engineers today - drift of time alignment between the analog and HD-1 audio. While the original algorithm can correlate audio that is already within 300 ms of alignment, the new TimeLock algorithm is capable of resolving up to 14 seconds of program diversity and is much more robust against processing differences and other artifacts.”

"Look Before You Leap"

"Elevated digital power will also aggravate self-interference to the analog signal. The level of self-interference will depend on several factors, including receiver bandwidth, use of extended hybrid modes, analog deviation, crest factor reduction methods and multipath propagation. Self-interference affects primarily SCA subcarriers and stereo L–R reception."

"Best Implementation Scenario"

"Spectral regrowth can happen when HD Radio 'sidebands' mix with the primary carrier frequency and create spurious signals on second, third and fourth adjacent channels. The transmitter isolation issue involves the need to keep the analog FM signal out of the HD Radio transmitter where it can create spectral re-growth problems. Isolators can be used to increase the isolation to the HD Radio transmitter, but the initial estimates on the amount of isolation required to prevent spectral regrowth appeared to be off by an order of 10 dB or so. Additionally, finding an isolator with sufficient power handling and isolation in the time frame we needed was questionable."

"I-Bust or H-Doomed"

"In these trying times, it should be pointed out that in most cases adding IBOC dramatically increases electric bills. I did three build-outs in Indianapolis and it almost doubled the power bills for the transmitter sites. Multiply this across the board and it is untold thousands of dollars a day going up in heat. If IBOC carriers were turned off, a lot of jobs could be saved with that money."

"IBOC in the Canadian FM Radio Environment"

"For a variety of reasons relating to the time requirements for digital signal processing, it takes 8-10 seconds for the digital audio signals to be heard when an HD Radio receiver is first tuned to a transmission. Likewise, it can take equally long to restore digital quality when the signal fails and then returns again. A secondary consequence of this processing delay is that programming fed to the analog FM transmitter must be delayed by 8-10 seconds whenever the blending feature is being utilized. This ensures that content is not lost when the receiver switches back to analog mode during a digital signal failure. Stations using this technology may need to implement certain internal operational changes to accommodate the fact that off-air listeners will experience delays of up to 10 seconds with both the analog and digital versions of their programming. Since no analog program version exists for ancillary HD2 or HD3 programming, listeners experiencing digital failures must simply tolerate audio outages until the signal restores itself."