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Comment by woodruffw | Hacker News Reader

This seems like a strange hill for automotive manufacturers to take a stand on: I can't imagine that the bill of materials for the AM radio is anything but tiny.

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I believe the issue is more that the increasing amount of EM noise in the AM band from electric auto components (particularly EV power inverters) means they would have to invest more engineering in to filtering that noise out.

That's helpful context, thank you!

That's the reason, yes. That makes cars mote expensive.

On the other side there are levels for unwanted radio emissions, how do the cars pass them? How do cheap cell phone chargers pass them? Or is nobody looking at this?

Compliance can be easy if you're designing a form of Faraday cage. Just make sure the car captures enough of the noise within its frame and you've got a pretty good start. Your car will comply with most (far from all) EM regulations as long as it doesn't disturb things outside the car.

The AM radio exists within the car. It probably even exists within the parts of the car that normally just get a metal box around it to shield the components. It's also very sensitive by its nature.

It's hardly an impossible feat, but car manufacturers will save every penny they can. Pretending to be "on your side" against the damn oppressive government forcing them to build provisions for areas without cell reception will probably also score some points with the public which mostly lives in areas where you don't need AM radio for important information.

> Compliance can be easy if you're designing a form of Faraday cage. Just make sure the car captures enough of the noise within its frame and you've got a pretty good start. Your car will comply with most (far from all) EM regulations as long as it doesn't disturb things outside the car.

This complies with existing regulations. The proposed regulations state the AM radio needs to work from within the car. So this wouldn't be sufficient according to the proposed rules.

> It's hardly an impossible feat, but car manufacturers will save every penny they can.

Good? I don't want to pay a tax on every new car purchase in order to subsidize owners of AM spectrum and their rapidly dwindling customer base.

> The AM radio exists within the car. It probably even exists within the parts of the car that normally just get a metal box around it to shield the components. It

When I was young I remember mopeda creating interfernces as far as 500 meters from the TV antenna. Car manufactureres managed to completely quieten that RF noise. So I would say it's doable.

> On the other side there are levels for unwanted radio emissions, how do the cars pass them? How do cheap cell phone chargers pass them? Or is nobody looking at this?

Regulators do pay attention to automotive components. I'm sure some of the cheap chargers don't bother with FCC Certification Testing.

The TL;DR is that unintentional and even intentional radiation must remain under certain field strength and/or power limits. That's why you're allowed to use those little aux-to-FM radio dongles to transmit on licensed spectrum, for example.

A "useful lie" explanation of the rules goes something like: "If the interference generated by the car stays within a very small radius (say, the car itself, or less than a few meters around the car) then the FCC doesn't care."

> How do cheap cell phone chargers pass them? Or is nobody looking at this?

You will build a prototype with all the filters and let it pass EMI tests in national laboratory. Then you will start supplying consumers with much cheaper electronics but in same package like your expensive prototype. Who is going to look into ultrasound welded plastic box? Nobody.

> means they would have to invest more engineering in to filtering that noise out.

Maybe they could take some of the money they're wasting making horrible things like touchscreen controls and use that to do some useful engineering instead.

And here I was, thinking they all did touchscreens because they were way cheaper and can easily work across different car models

Yes, I should have said "actually useful to the customers".

I'm with you on that

What are the customers going to do, buy someone else's car that also has a terrible touch screen from the same manufacturer?

American businesses are hell bent of ignoring anything but the dollar sign at the bottom of the balance sheet, and since they all use the exact same value and prioritization system, they can all do the exact same thing without technically colluding, preventing any consumer from ever doing the free market thing and buying something better.

> What are the customers going to do, buy someone else's car that also has a terrible touch screen from the same manufacturer?

Well, what I do (not only because of this, but those touch screens certainly contribute) is to not buy new cars.

Volkswagen have RCD head units that are compatible between VW and Škoda cars. RCD/RNS 210, 300, 310, 320, 330, 360, 510, 560, etc are all interchangeable and some are touchscreen-based, others are button-based. I think they also do the same for SEAT and Cupra cars, though head units have different models.

I'm not so sure compatibility with the car is the reason. Maybe it's more about maintaining one branch of software for more head units.

> […] means they would have to invest more engineering in to filtering that noise out.

Wouldn't this mostly be a one-time charge, and then just cookie-cutter the solution going forward?

(I say this as someone living in Toronto, Canada, where we have streetcars/trams with overhead wires, which play havoc with (AM) radio when they go by.)

Good. With a fairly modest amateur radio setup I can pick up electric and hybrid cars moving around half a kilometer away, without really trying.

This is not about the BOM for AM radio components. It's about sidestepping the R&D costs and BOM costs of the stuff needed to keep electric motors, switching power supplies, etc. in new electric vehicle products from murdering the low end of the radio frequency spectrum.

The radio costs very little, but the antenna needed for AM has to be much larger than for FM to get similar performance. I can imagine that auto manufacturers would love to get rid of the cost of installing the antenna by only supporting Bluetooth.

AM radio antennae of the ferrite coil or rod variety are tiny and have been in widespread use for over a century.

http://www.hard-core-dx.com/nordicdx/antenna/loop/amloop.htm...

If locating it within the electric vehicle's superstructure is not suitable to the manufacturer it is not difficult to put one in a stubby sharkfin roof mounting as is done with GPS, mobile phone, and satellite radio antennae.

to the best of my knowledge, the issue is EVs emitting frequencies that interfere with AM radio, so instead of adding shielding or figuring out how to retain the integrity of the AM signal, they've opted to just remove the antennae all together.

You can't sell AM radio subscriptions, I would imagine the demographic that listens to AM would likely pay for something in its place.

Originally it was a diode, a coil and a speaker. They're more complicated these days. But yes the attraction was simplicity.

If you want a challenge, implement a superheterodyne signal processing stack in GNUradio or python.

Seems odd to let businesses and manufacturers determine their own pricing incentives to you?

Consider how this will silence Conservative talk radio and it might then make sense.

The co-sponser of the bill interviewed for the article is a Democrat, so this doesn’t seem politically motivated.

If you're referring to the far right rabble rousing, that's also on FM these days. It doesn't really make sense to refer to a movement trying to tear down US institutions as "conservative".

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