FCC OKs Increase in HD Radio Power. Increased Interference Ahead?
On Friday the FCC’s Media Bureau quietly announced that it adopted an order to allow FM stations broadcasting a digital HD signal to increase their power levels up a maximum of 10% of the power of their main analog signal. While the National Association of Broadcasting and iBiquity have been agitating for this change for quite some time, it’s the backing of National Public Radio and its engineering report on the matter that was the likely tipping point.
But, as radio researcher John Anderson points out, this change is also likely to produce more interference complaints from listeners trying to tune in weaker stations adjacent to these higher power digital signals. There have already been significant complaints and concerns about digital HD signals interfering with adjacent analog stations with the previous power limit set at 1% of a station’s analog power.
The Prometheus Radio Project, in particular, questioned NPR’s support for the increase based on NPR’s own engineering data (PDF). Prometheus noted that listeners asked by NPR Labs to rate HD interference to analog signals at the new power levels gave the quality of the resulting audio a score of 2.7 on a 5 point scale, which is below a rating on “fair” on that scale. Prometheus further argued that,
The NPR Labs Study represents a “best case scenario” test of interference to analog. … Although the NPR Labs Study showed troubling levels of interference, the decision to use a single, highly selective receiver dramatically limited the extent to which these results can be extrapolated.
For its part, NPR responded to Prometheus and other critics [PDF], contending that they “generally misapprehend or ignore the [HD] testing methodology, the test results, or the results of NPR Labs’ prior [HD] testing.”
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