With FM IBOC, one thing that’s been a little disappointing for stations is that digital coverage doesn’t go as far as the analog signal in some cases.
I’ve been hearing scuttlebutt for awhile about getting the FCC to approve a 10 dB increase in the FM IBOC power level; currently digital is set to –20dB below the analog.
I asked Struble about this; he said the company is looking at a variety of ways to extend system coverage, though there’s nothing Ibiquity is ready to publicly talk about yet.
One clear way coverage is improving, Struble said, is that performance of HD Radios is getting better compared to the initial generation of receivers.
Stations could try increasing power level, he said, but he didn’t comment on whether that’s recommended.
One engineer told me the trick is to find the appropriate higher power level and yet avoid host interference to the analog carrier from the co-located digital subcarriers — and without negatively affecting another sought improvement, digital boosters. Other OFDM technologies, such as satellite radio, benefit greatly from digital boosters, which would act as terrestrial repeaters do, he said.
“Considering digital boosters on their own, [broadcasters] already have some concerns about host interference, since it is easy to imagine a situation where the analog main signal is weakened, and the digital booster steps in with its extra power and the digital/analog ratio is screwed up,” according to this engineer, who is not with Ibiquity.
“If you increase the digital power by 10 dB, you will get increased HD Radio range … but know that you may want to think carefully before turning on any digital boosters.”
