In-band, on-channel digital audio broadcasting (DAB) increases in...
In-band, on-channel digital audio broadcasting (DAB) increases interference to analog subcarrier (SCA) operations by average 2.6%, according to study for NPR and International Assn. of Audio Information Services (IAAIS) that was submitted to FCC. Study indicated interference levels ranged…
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from 0.3% in areas with flat terrain and high signal power to 8.5% in L.A. market. SCA is used for variety of data services, primarily including reading services for blind. Most of new interference is from secondary adjacent channels, report said, with first adjacent channel IBOC interference apparently effectively “masked” by analog interferer. Meanwhile, in separate FCC filing, IAAIS said there was “no industry-wide plan to bring reading services from analog subcarriers into the digital transition” until end of hybrid analog-digital phase. As result, it said, SCA must accept some increased interference, with some consumers unable to receive acceptable service level. IAAIS said some of problem could be resolved by devoting more of digital bit stream to SCA-type services, but there’s “no testing scheduled” for that. It said FCC had “correctly characterized” such reading services for blind as “existing broadcasters” that must be protected during DAB transition, so IAAIS said Commission should act to actually protect service from debilitating interference.