HD Radio AM encourages 100% digital transmission and the abandonment of hybrid mode

Challenges of HD Radio AM Hybrid Mode Transmissions

The challenges of HD Radio transmissions in AM hybrid mode have never been convincingly overcome. The coexistence issues between analog and digital signals are like a divorced couple forced to live together. Range, stability, and other well-known limitations are still present, a battle that has lasted for years.

Xperi, the company that owns the HD Radio system, has increasingly encouraged broadcasters to transition to all-digital transmissions. And it makes sense, doing so would eliminate the "cohabitation" problems between analog and digital signals.

https://hdradio.com/all-digital-am/

Why Would a Station Stop Broadcasting to Part of Its Audience?

The hybrid system allows AM broadcasters to reach both listeners with high-quality HD receivers and those with basic analog radios. However, operating in hybrid mode means reducing the power and quality of the digital signal. This limits coverage and the potential for better sound. Switching to 100% digital enables higher transmission power and higher bitrates, directly improving both range and audio quality.

It's a trade-off: being compatible with all radios but offering a weak signal, or offering excellent quality and strong range, but only for digital receivers.

Coverage Comparison: Analog vs. Hybrid vs. MA3 All-Digital

Transmission Mode	Daytime Coverage	Nighttime Coverage	Robustness / Noise Resistance
Analog AM	Traditional contour (0.5 mV/m)	Similar, with high noise	Highly susceptible to interference
HD Radio Hybrid (MA1)	Smaller than analog	Vulnerable to digital dropouts	Side-channel interference
AM All-Digital (MA3)	Equal or better than analog	Stable up to coverage contour	Significantly better noise resistance

Never a Fan of Hybrid Transmissions

When hybrid tests began in Brazil around 2005, the results were not promising, and I already suspected they wouldn’t be. Twenty years later, conclusions are aligning with what I, from rural Brazil, foresaw back in 2005. Now there's growing support for full-digital AM transmissions. Hybrid issues also affect HD Radio FM, but not nearly as severely as in the AM band.

https://hdradio.com/all-digital-am/

Not a New Push

The push for voluntary adoption of all-digital transmission has existed for years. But the greater the adoption, the better HD Radio can perform, eliminating digital/analog coexistence issues, which often damage both signals.

The Hybrid Dilemma: A Slow Transition

Hybrid mode enables transition but also slows it down. It becomes convenient to tolerate hybrid-born problems. But at some point, without moving forward, those limitations prevent the system from reaching its full potential.

HD Radio AM All-Digital (MA3)

1. Audio Quality

   • MA3 mode delivers near-FM stereo quality, free from typical AM noise like hiss and electrical interference.

   • It supports metadata (program info, album art, station logos).

2. Signal Robustness

   • Without the analog carrier, the full bandwidth can be used for digital, improving coverage and reliability.

   • WWFD 820 AM in the U.S. showed stable digital reception in areas where analog failed.

3. Spectral Efficiency

   • All-digital signals are less prone to adjacent-channel interference, reducing spectrum pollution.

Why It Still Isn't Widely Adopted

1. Small Base of Compatible Receivers

   • Few listeners own AM radios that support HD Radio.

   • Most HD Radio-equipped cars focus on FM; few support AM-HD.

2. Risk of Losing Audience

   • Turning off analog immediately alienates all users with traditional AM radios—a major commercial risk.

3. Transition Costs

   • Even without needing a new transmitter, MA3 requires reconfiguring the transmission chain, antenna adjustments, and licensing from Xperi.

Current U.S. Adoption (2025)

Situation	Status
FCC Authorization	Approved since Oct 2020 (voluntary)
All-Digital Stations	Fewer than 10 actively operating
Success Case	WWFD 820 AM (now WSHE)
Trend	Low adoption, testing continues

Lower Adoption Than FM

HD Radio adoption in AM is far lower than in FM. The hybrid mode severely degrades analog while providing little digital benefit, making the two signals more adversarial than complementary.

What About Brazil?

Brazil is currently not on Xperi’s radar, at least not officially. Any approach would likely require negotiation between governments. Brazil's federal government tends to resist foreign proprietary tech that creates royalty dependencies. The U.S. remains Xperi’s main growth market. While Brazil could be a great business opportunity, there’s no sign of active pursuit.

A Geopolitical Bargain?

A potential shift could happen if the U.S. offered Brazil trade benefits in exchange for adopting HD Radio. For example: mandatory inclusion of AM/FM HD receivers in all new cars. Such a deal could make Brazil an attractive, captive market for Xperi.

However, DRM (Digital Radio Mondiale) is more open and less risky for Brazil. HD Radio’s commercial success would likely require mandates for automakers—again, something the U.S. would push for in any negotiation.

Among All Systems, HD Radio Is the Most Profitable

Compared to DRM, HD Radio is more commercially self-sustaining. Its business model benefits those who control it: royalties and licensing create a scalable revenue stream for Xperi. Expansion means recurring profit.

I’ll explore that power dynamic further in future posts.

Comparison: HD Radio AM MA3 vs. DRM AM

Criterion	HD Radio MA3	DRM (Digital Radio Mondiale)
Audio Quality	High, near FM stereo	High, including stereo and surround
Range	Good, but abrupt cutoffs	Greater, with smooth transitions
Receiver Availability	Scarce for AM	Also limited, but growing
Licensing	Proprietary, paid to Xperi	Open, free (royalty-free)
Shortwave Support	Not compatible	Fully compatible

Technically solid and functionally strong?

HD Radio AM all-digital (MA3) is technically solid and functionally strong. It delivers excellent sound and robustness. But for most AM stations, it's still commercially unfeasible due to limited receivers, audience loss risk, and transition costs.

So, it hasn’t become the dominant standard, but remains a promising option for specific markets ready to innovate.

HD Radio Is Just One Piece of the Puzzle

Xperi knew it had to be more than just radio. It turned HD Radio into part of a broader multimedia package—integrated into homes, cars, and lifestyles. It's a mistake to see HD Radio as a standalone. It's now bundled with DTS, IMAX Enhanced, and TiVo, especially focused on the car dashboard experience.

Political powers

I extend the topic beyond HD Radio's 100% digital AM to a global overview of all adoption movements worldwide for AM and FM, whether in the HD Radio, DAB, or DRM standards. There are complexities involved in advancing any of these standards that relate to politics, whether they are interested or not in being political agents.

There are so many innovations and complexities involved in implementing one or more systems aimed at digitalizing AM and FM that, at this moment, I don’t see our government having any real focus on the matter—let alone a comprehensive understanding of it.

Only if this issue were to gain geopolitical relevance in the economic sphere would we likely see progress in decision-making, whether in favor of DRM or HD Radio. For now, not even DAB is on the table. Mercosur hasn't negotiated, nor even considered facilitating its products' access to Europe through agreements tied to DAB adoption here.

Economics cannot be separated from geopolitics, and technical standards will either be used as instruments within this context or will become active agents of it.

Back to the Future

What about the success of the request for adoption of purely digital transmissions? From various sources, I see that the adoption of 100% digital mode in HD Radio AM in the United States has very low uptake. Is this the expected result due to the conditioning promoted by the hybrid system, which has been inefficient so far? You end up deteriorating the AM environment for years, and any new change brings great insecurity to the broadcasters themselves, who have seen the low efficiency of hybrid transmission discourage audience adoption of the digital signal. They end up fearing the abandonment of "analog" listeners.