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IBOC Critic Opposes Power Boost

Damage to the FM service seems 'irrefutable,' McLarnon tells the commission.

Canadian engineering consultant Barry McLarnon opposes a power increase for IBOC in the United States and says the Federal Communications Commission should dismiss the idea.

In comments filed with the FCC on the proposed 10 dB increase, McLarnon says at issue is whether a power boost will cause an unacceptable decrease in the useful coverage of adjacent analog FM signals.

Predicted interference calculations using computer modeling software is valid and such results should be refined with field-testing, as NPR Labs did with its tests, he said. He called the NPR report “compelling” and that it points out not even the current IBOC power level at 1% of the analog is “far from problem-free” and that interference is likely under-reported “due to the noise-like nature of IBOC-to-analog interference, which lacks the audible clues of typical analog-to-analog interference.”

A conclusion seems “irrefutable” that a 10 dB digital power increase would severely damage the FM service, according to McLarnon.

By contrast, the iBiquity approach was to conduct testing “on a very small number of stations, decide which situations may result in a significant increase in interference at the higher IBOC power level, and then attempt to extrapolate that conclusion to the entire country,” he wrote. He found anomalies in iBiquity’s test results and generally criticized the testing methodology.

Comments are due to MM Docket 99-325 on Nov. 28.