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Comment by galleywest200 | Hacker News Reader

Where I live we have signs up all over the place near the mountains that tell you to tune into a specific AM station when flashing for avalanche/weather information. I understand wanting to move past some technologies but we are not going to be able to revamp our entire avalanche system _tomorrow_.

Most people I know do not have a short-wave radio, let alone one capable of receiving at 162Mhz.

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Personal anecdote: that actually saved an important doctor appointment. "URGENT MESSAGE WHEN FLASHING". Well, lights were flashing, guess we could tune to it and hear what it has to say. Sure enough, it announced a traffic jam on our route a few miles ahead that Google Maps vastly underestimated (usually it's been good about that) and we were able to avoid it. Thanks TNDOT.

It was because a chemical truck crashed apparently, on our drive back home it was still there with specialized hazmat emergency vehicles around.

162MHz is VHF, shortwave is much lower frequency (and longer wave).

More or less all US car owners already own a VHF radio. Extending it from 88-108MHz up to 162MHz would be fairly trivial.

Retro fitting all previous car & upgrading all am based equipment is not however

Why not broadcast it as FM? Much better signal, much less chance that somebody misses a word because AM quality is shit.

AM covers a larger area, and is more robust in areas with obstructions (e.g. mountains).

Yeah, I remember as a kid with a Cheap stereo and an antenna consisting of maybe 5ft of thin wire dangling from it being able to pick up reasonably clear AM transmissions from as far away as St Louis, Chicago, and NYC… and Inlived in almost-coastal NC. Especially at night you could really pull some stuff in.

FM by comparison is effectively line of sight, so with a practical broadcast antenna the upper limit is 40 or 50 miles.

the am antenna in your cheap stereo was probably not the dangling wire, but rather a ferrite rod hidden inside the case

Pretty sure it was the wire, because changing how it was aligned would affect what could pick up pretty dramatically.

And I should clarify… while it was certainly a cheap “system in a box”, it was a real multi component system with detachable speakers, etc. not a boombox or anything like that.

"AM" is the modulation scheme. A more accurate name for this radio service is used in Europe, "middle-wave".

The modulation scheme is not the reason for propagating around mountains and bouncing off the ionosphere at night. The reason for that behaviour is the low frequency used. 540 Kilo-herz to ~1700 Kilo-herz. (I was told once by a young engineering colleague that 1,000 Khz was not RF. :-))) )

So the question is valid. FM could be used in the "middle-wave" band. It would reduce noise but might suffer more when bouncing off the ionosphere at night. (I have read this but never heard FM bounced)

The reason FM is not used in the middle-wave band is legacy regulation not technology.

Fm also takes 10 times the bandwidth of am of that spectrum. The blocks are where they are for a reason.

FM takes whatever bandwidth you allow it. The harder you hit it the wider it goes. The limiting factor is when modulation exceeds the bandwidth of the receiver, it clips very badly.

Narrow band FM is used for aircraft. police, fire, amateur radio communication and since 2021 it's even legal for CB radio in the USA. It's deviation is limited by law to about +/-2.5KHz, from centre frequency.

Setting up the modulation depth on an a broadcast FM exciter, I have used a spectrum analyzer and Bessel function information to make sure it was legal.

" (I was told once by a young engineering colleague that 1,000 Khz was not RF. :-))) )"

I've alluded to this elsewhere. As I mentioned, RF/RFI and spectrum management subjects have been downgraded or reduced in electrical engineering courses just about everywhere so it's little wonder we've problem.

Bandwidth in part.

AM is more spectrally efficient than FM, and with synchronous AM receivers, you can get noise rejection that is near FM.

Noise reduction in this scenario would be performed the obvious way - by looping the message.

I THINK it is FM, narrow FM. My SDR receives some attenuated incomplete-sounding signal when switched to AM on 162.55 MHz even if I widen the bandwidth, and switching to narrow FM gets me the same clarity and volume as my actual weather radio provided I lower the gain a little.

> Where I live we have signs up all over the place near the mountains that tell you to tune into a specific AM station when flashing for avalanche/weather information.

I live in an area like that as well, and the station broadcasts the same info you see on road signs and web sites. If the lights are flashing it's usually playing "snow tires advised for vehicles..." on loop.

the kind of situations people describe where car AM radio is essential feel like corner cases that involve lack of planning and poor judgment or really bad luck. No cell service, no portable radio in your travel kit, no way to stop and ask anyone, and you can't just turn around when you see a flashing sign? It sounds like the plot of a horror movie.

That’s YOUR area. Plenty around here without any giant flashing signs. Also long 100km bits of highway without cell service

Thing about corner cases is they do exist and need to be accounted for

So, cars in YOUR area should have AM radios? But not every car in existence needs one?

Cars tend to move around

NIMBY!

If you actually lived out in the country you'd know that there's like a dozen portable AM radios per household and that nobody ever just guesses about pass conditions. Every scenario people come up with involves a hypothetical hayseed who's almost aggressively unprepared for his situation.

This is a problem solved by a $10 Amazon purchase. Why is it such a crisis for you?

People who don’t live in these areas often drive through them to get from point a to b.

Personally I think it’s pretty ridiculous for cars to be removing it and it’s taking a law to force them to keep am radio

But that’s besides my point

How much more convenient than a $10 Amazon purchase does access to emergency AM need to get?

Would having each new car come with a portable AM radio in the glove box be an acceptable solution? What if car AM came locked to an emergency government frequency?

From my perspective we're looking at broadcasters cooking up culture war so they don't have to negotiate with the auto industry to keep their business running, and the end result will just be increased car prices for everyone.

If the car is putting out to much EMI to make it expensive to put that 10$ radio into the dash with the FM one the handheld will be just as useless.

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