Car radio interference issues may be solved without having to remove all of them-EEWORLD

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With all the streaming media entertainment available in cars, the radio that was once standard in cars seems a step behind the times. AM radio can easily be classified in the hallowed category of "perfect technology." It has been around for more than a century, but its design has not seen any major technological advances in at least a few decades.

Why are car manufacturers phasing out AM radio?

Some automakers have said they intend to no longer offer AM transmissions in their cars because electromagnetic interference can cause static and noise that annoys customers. Perhaps it's time to gracefully end this legacy technology that no longer has much use. Yet AM radio remains widely used in many parts of the world, including the United States, and plays an important role in daily life and emergency communications for hundreds of millions of people.

Despite much outcry, the phase-out of AM radio in electric vehicles has been underway for some time — BMW decided not to include the technology in the 2014 i3. "In order not to frustrate our customers with poor reception and loud noise, we have decided not to include this equipment (AM radio) in vehicles equipped with eDrive technology," BMW said in a statement, referring to the system that powers its electric vehicles.

But the trend has accelerated in recent years. In March, Massachusetts Senator Ed Markey surveyed 20 automakers and found that eight of them — BMW, Ford, Mazda, Polestar, Rivian, Tesla, Volkswagen and Volvo — had removed AM radio from their electric vehicles. Ford also intended to remove radio from its gasoline cars by 2024, but recently reversed that decision.

As more electric vehicles ditch AM radio, broadcasters are calling it a worrying shift that could spell trouble for stations and deprive drivers of a key source of news in emergencies.

The problem isn’t the car’s battery itself, but the current that drives the motor. “The current system is the vehicle, and a lot of it is pulse-width modulated,” said Ashruf El-Dinary, senior vice president of digital platforms at Xperi. “So it has some high current running through it, which creates inductance, which can be transferred back to the antenna system.” This can create unwanted noise throughout the AM band, especially in the lower part (between 500 and 700 kilohertz), which manifests as a buzz or hum.

Part of the problem is that there isn’t enough data to fully understand the issue, either. “There isn’t a lot of measured data on electric vehicle interference in the AM radio band,” Zamir Ahmed, vice president of communications for the National Association of Broadcasters (NAB), said in an email to IEEE Spectrum. “In general, some electronic devices will generate interference on discrete frequencies or clusters of frequencies, while interference from other devices can affect the entire band.” NAB launched the “Depend on AM Radio” campaign in April to raise awareness of the issue.

It turns out that electric car batteries and motors aren’t the only cause for concern for AM radio—they’re just the most notable of a long list of culprits. “There are other noise influences,” El Dinary says. “Even power windows or power mirrors in a standard car can affect analog reception if they’re not designed or shielded correctly.”

Correctly shielding an entire electric vehicle system is certainly more complex and expensive than properly shielding a power window system. If it is not done correctly, the consequences are more obvious. Therefore, most manufacturers choose to remove the AM radio completely rather than go to the trouble of further redesigning their vehicles.

Volkswagen, for example, has said that changes needed to incorporate protect AM radios from the electrical current will result in extra weight that would reduce a vehicle’s range. Stellantis, the parent company of Chrysler and Jeep, one of the few manufacturers to address the issue, is using shielded cables and moving radio receivers away from the engine in future cars. (Stellantis did not respond to a request for comment on more details of its mitigation strategy.) “If you’re talking about pure amplitude modulation, that hasn’t changed in 100 years,” El Dinary says. “I think radio designs matured pretty well about 15 years ago when they moved into more of the [digital signal processing] world where the demodulation or decoding was done at the software level.”

Perhaps the common perception of AM radio as an old technology that has been through its development cycle has led automakers to believe it's not worth including because it doesn't match up with the latest innovations. But this ignores the fact that about 47 million Americans still listen to AM radio, and in rural areas it's often one of the few options.

That’s not to say there aren’t still some advances in the world of AM radio. One of Xperi’s products is HD Radio, which allows AM stations to broadcast both analog radio transmissions and digital radio transmissions that carry all the data of a modern infotainment system: song titles, album art, station logos, and so on.

El Dinary, who has worked with HD Radio for 25 years, says he's heard of some AM stations choosing to shut down analog transmissions entirely in favor of going fully digital. That could be one path forward: "Our extensive testing has shown that digital broadcasts can survive in this noisy environment," he says. Even so, he stresses that HD Radio is not meant to completely replace AM radio, but rather a backwards-compatible evolution.

Whether it’s a transition from AM radio to HD radio or something else entirely, it’s still unknown. However, perhaps automakers will find a way to still keep AM radio in electric vehicles. Not only because of its age, but in a hurricane, wildfire, or any other emergency, simple, reliable technology is still the best way to help people get the situation.

“In a crisis, there are a lot of vulnerabilities in cell phone towers, and even FM radio,” El Dinary said. “TV is promising, but it’s not that portable. If people are trying to evacuate an area or need to get moving to find gas or food or whatever, they can figure that out in their car — that’s where we want them to get the information.”

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