With little fanfare on Friday, the FCC approved a blanket four-fold increase in the power of FM-HD digital sidebands, and also established procedures for stations to apply for a power-hike of up to 10x.
This outcome was no surprise. For the last two years the proprietors of HD Radio, iBiquity Digital Corporation, and National Public Radio have been wrangling over just how much of a digital FM power boost is needed to replicate existing FM stations’ analog coverage.
The problem is, even with all of the claims of HD’s proponents (on the record, no less) that a fractional-powered FM digital signal can provide the equivalent coverage area of a full-power analog signal, reality has proven disturbingly different. Not only are FM-HD signals difficult to acquire and lock onto on a mobile platform for the long haul, but the signals fail miserably at penetrating buildings.
The FCC and HD Radio’s proprietors believe this is the primary reason why the adoption of FM-HD broadcasting “has dropped significantly over the last two years.”
The FCC’s 
latest digital radio Order is notable for four whoppers. The first is that, as predicted, NPR’s technical analysis was used as a foil to both approve the power hike and pooh-pooh any concerns of increased interference from the increase in digital FM power. It provided neutral political cover for a questionable technical decision.
The second was the optimistically-projected lack of expected interference from the move: “Based on our analysis of…data, as well as five years of interference-free FM hybrid digital operations by approximately 1500 stations,” the FCC blesses the FM-HD power hike.
The record does not reflect this conclusion. Not only has the FCC received several complaints from listeners in its ongoing digital radio proceeding about interference between digital FM sidebands and nearby analog signals, but the potential amount of interference between the “host” analog signal of an FM-HD station and its digital sidebands is likely to increase because of this Order. This was noted more than a year earlier – by one of the architects of NPR’s preliminary power/interference studies, no less.
The third whopper is the FCC’s callousness toward what higher-power FM-HD sidebands will do to the reception of nearby LPFM stations. Public-interest lobbyists pressed the FCC just earlier this month to take an incremental approach to any FM-HD power increase, noting the FCC’s promises to look into an expansion of LPFM service.
The rub is that, under the FCC’s latest decision, any full-power radio station may conduct FM-HD broadcasts at digital power levels well in excess of what any LPFM station is allowed to broadcast with in analog alone. In a nutshell, the increased power of FM digital sidebands constitute a clear and present danger of interference to the reception of LPFM stations. The FCC blew that off: “As a general matter, adoption of these recommendations would constitute a dramatic change in LPFM licensing rules and the relationship between LPFM and full-service stations. Analog LPFM and FM translator stations are secondary services, and, as such, are not currently entitled to protection from existing full-service analog FM stations.”
Thus, any potential material growth of LPFM is now directly dependent on just how much the interference noise-floor on the FM dial increases because of the proliferation of higher-power digital sidebands. The answer to this quandary will only become known with time.
Finally, with regard to any increase in digital interference, the FCC’s Order recommends that the conflicting stations first try to rectify the matter between themselves. If this is not possible, the FCC may be called upon to mediate interference concerns, but only if the aggrieved station applies for relief, and only if the complaint contains
at least six reports of ongoing (rather than transitory) objectionable interference. For each report of interference, the affected FM licensee must submit a map showing the location of the reported interference and a detailed description of the nature and extent of the interference being experienced at that location….The complaint must also contain a complete description of the tests and equipment used to identify the alleged interference and the scope of the unsuccessful efforts to resolve the interference.
If the interference-appeal meets this onerous criteria, the Media Bureau promises to act upon it within 90 days.
Speaking of dramatic changes, this aspect of the digital radio rulemaking puts the burden of proof of harm on the station(s) receiving interference, not the station(s) causing it. FCC spectrum-management rules, with the exception of secondary services (like LPFM) are generally written in such a way that a new service will, by design, work to minimize its impact to nearby spectrum-neighbors. This new FM-HD interference rule not only flips that paradigm, but encourages interference by discouraging stations to report it.
Still and all, this is not likely to jumpstart a second wave of FM-HD station implementations; it’s questionable just how many stations will invest in a digital power increase anyway, given that it involves some rather substantial reinvestment in a station’s transmission plant.
The fault of FM-HD radio is not in a single technical tweak; it’s in the design of HD Radio itself, which overpromises and underdelivers to the detriment of existing analog services. The fact that the FCC is so willing to sacrifice the integrity of analog radio for a crippled digital replacement is deeply disturbing.
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