[stu2010]

I haven't seen much discussion about how AM gets used for local road condition or emergency communication. When you're driving and see a sign that says "TUNE TO 1610 AM" and the car has no AM receiver, what do you do?

This may be a shrinking niche, but it's potentially a last bastion of AM radio usefulness.

[RF_Enthusiast]

Those low power highway information stations are actually required to be low quality audio [1]. My understanding is that back in the day, broadcasters insisted that these stations were low quality so they would not compete with commercial broadcasters.

In my opinion, those stations actually make AM seem much worse than it really is. That scheme backfired in the long run.

[1] 47 CFR 90.242(b)(8) <https://www.ecfr.gov/current/title-47/chapter-I/subchapter-D...>

[Scaevolus]

TIS stations have low-pass filters from 3-20kHz, but it looks like most AM stations have low-pass filters from 5-20kHz anyways to avoid interference with neighboring channels: https://casetext.com/federal-register/audio-filtering-requir...

[Fatnino]

There was (is?) a commercial station in the bay area that broadcasts simultaneously on AM and FM. I could tune the car radio to the correct frequency on each and then compare the sound quality by flipping the AM/FM switch.

FM is WAY better sound quality. It's not even close.

[aidenn0]

What about sports broadcasts? I often listen to games in my car on AM.

[RF_Enthusiast]

As do many people. AM stations that run play-by-play sports programming do very well in the ratings, and do very well with the station's sales team.

[quickthrower2]

Tunnels near me just say "Turn on your radio" and blast the whole FM spectrum at least (might try it with AM too!). Guess you can do this in a tunnel!

[RF_Enthusiast]

Fun fact! In the US, a Tunnel Radio System may operate in any mode on any frequency provided the signal does not leak from the tunnel[1].

[1] 47 CFR 15.211 <https://www.ecfr.gov/current/title-47/chapter-I/subchapter-A...>

[Analemma_]

In a sample size of maybe 10, every time I’ve seen one of those highway signs and tuned to the station, the quality was so bad I couldn’t make out any words and so got no useful information. If that’s the last bastion of AM usefulness, scrap it and give that spectrum to the wireless carriers. Frankly, for stuff like road closure information I’m a lot more likely to get that from Waze (delivered over a 5G connection) now anyway.

[tjohns]

The wireless carriers wouldn't be able to do anything with the AM broadcast band. It's in the MF range - not useful for cellular at all due to limited bandwidth, giant antenna requirements, and ionospheric bounce.

[RF_Enthusiast]

I don't think wireless carriers would want 1.2 MHz at that low of a frequency. They'd have the same issues with interference that broadcast stations have. The transmit antennas would take up acres of land (each element hundreds of feet long). Receiver antennas would also need to be large.

Also, very little data would fit in such a tiny spectrum window.