HD Radio's Adoption Curve and the Absent Switch-Off Date

A Licensed Standard, Not a Mandate

HD Radio, the in-band on-channel (IBOC) system developed and licensed by iBiquity Digital Corporation, layers a digital signal alongside an existing FM or AM carrier within the same frequency allocation. A receiver that understands the digital layer plays it; one that does not hears ordinary analogue. The design was deliberately non-disruptive — no new spectrum, no forced hardware replacement, no switch-off to plan around.

The FCC authorised HD Radio for FM (day and night) and AM daytime operation in 2002 and extended AM nighttime permission in 2007, making the United States one of the earliest markets to deploy a hybrid digital system at scale. But the architecture that made adoption politically easy also removed the mechanism that would eventually force a transition: because analogue never turns off, there is no deadline, and without a deadline there is no urgency.

Where the Numbers Sit

Edison Research, which publishes annual tracking data on American audio behaviour, has recorded steady but unspectacular growth in HD Radio receiver ownership. By the mid-2020s, the Infinite Dial survey placed in-car digital radio tuner penetration well below the figures European markets achieved after setting firm FM end dates. The contrast with Norway — which completed its national FM shutdown in 2017 and saw rapid, deadline-driven hardware adoption — is instructive.

The National Association of Broadcasters cites a cumulative installed base running into the tens of millions of receivers, concentrated almost entirely in the automotive sector, where manufacturers including General Motors, Ford, and BMW have bundled HD Radio chips as standard fitment on mid-range and above trims. Consumer electronics adoption — tabletop radios, portable sets — has remained marginal. The royalty structure iBiquity charges hardware manufacturers, though it has fallen over time, added a layer of resistance that DAB+'s open standard never imposed on European device makers.

The FCC's Non-Position

The FCC has declined to set an analogue FM end date. No formal rulemaking is pending. The Commission's posture, consistent across multiple administrations, is that a switch-off would require demonstrated receiver ubiquity and a public interest showing that the agency has not been asked to make. Major commercial groups — iHeartMedia, which emerged from Chapter 11 in 2019 carrying a restructured balance sheet, and Audacy, which filed for Chapter 11 in January 2024 — carry infrastructure debt that makes voluntary analogue exit a low priority. Analogue transmitters are already paid for; the case for accelerating their retirement is, commercially, weak.

The terrestrial-radio exemption compounds the stasis. Under current US copyright law, over-the-air AM and FM broadcasters are exempt from paying performance royalties to sound-recording rights holders — an entitlement that applies to analogue transmission and, critically, carries over to the HD Radio digital layer so long as it is broadcast as part of the same licensed service. A formal digital migration that extinguished the analogue signal would not, on its own, disturb that exemption, but any policy process around FM shutdown would inevitably attract scrutiny of the broader royalty framework. That is a fight the industry has consistently preferred to defer.

No Shortage of Signal, No Urgency

HD Radio functions well where it is deployed. Multicast subchannels allow a single licence to carry several programming streams on the HD2 and HD3 layers, and the audio quality ceiling is demonstrably higher than analogue FM at equivalent bitrates. The gap is not technical. It is structural: a system without a committed end date for its predecessor tends to occupy a permanent secondary status — available, improving, and never quite required. The Copyright Royalty Board sets webcaster rates on five-year cycles; the FCC sets no equivalent clock for analogue FM's end. Until it does, the HD Radio adoption curve will continue its gradual ascent toward a horizon that no regulator has yet marked on a map.