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Comment by mianos | Hacker News Reader

This assumes everyone has an AM radio. I don't have one in this household at all. I have no reason whatsoever to own one. It's not much use having an emergency transmitter when no-one has a receiver and even then, it's not running all the time. AM is probably worse as you need squelch or to keep transmitting a carrier to keep it quiet.

On the other hand most people have the facility to receive an SMS and most of them have their phone on. The only issue is lack of power to charge a phone. Worse than keeping an AM radio running but in the past people turned on their AM radio at certain pre-organised times of day anyway so there is not really order of magnitude difference between a phone and an AM radio.

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Disasters (natural or otherwise) are usually fairly localised. Cell towers have a reach of a couple km at best and can be easily overwhelmed, whereas AM radio can reach upwards of 100km at night from a single transmitter and doesn't care at all how many people are listening.

As you already mentioned, power is another issue, as a modern smartphone won't last past a few weeks, even when turning on for only 5 minutes once a day, whereas I've seen AM radios that can run continuously for at least that long.

Finally, my main concern: cell phones are complicated. An EMP (or flood) could fry all your electronics and you're basically screwed, but finding someone who can build a passable AM receiver (or even transmitter) out of various electronic junk isn't all that difficult.

You can build an AM receiver with just a coil made of wire, a magnet and some scrap.

There was an issue with flooding in Lancaster (a mid-sized English city) which had this exact issue. The report is a fairly interesting read: https://www.lancaster.ac.uk/media/lancaster-university/conte...

AM signals can reach much further than 100km at night, thanks to physical properties of the ionosphere. When I was younger, I remember driving long distances at night in rural New England and being able to pick up one of the big Chicago stations more than 1500 km away.

Commenters on this blog post about the phenomenon claim to have done much better with special antennas, e.g. picking up a station in Los Angeles from Queens, NY: https://news.ccrane.com/2018/07/23/why-am-listening-at-night...

This assumes everyone has an AM radio

I suspect that there are more AM radio receivers in the UK than there are DAB receivers. A couple of months ago, BBC Radio Devon was airing announcements asking for donations from people so that they could buy the poor and elderly new DAB radios because they only had AM radios. It seems to me that if a station to make it a big charity drive, there must be a reason.

Definitely not working ones. As someone who ran an AM+FM station for 5 or so years not that long ago, 99% of listeners were FM, with very few AM listeners.

In another life I did work on broadcast censorship circumvention into places like China etc; the main concern at the time was that shortwave radios were becoming rare enough to make the traditional big SW/AM TX near borders kind of irrelevant, so focus was moving to online - Tor, et al - because people actually had that tech.

> Definitely not working ones. As someone who ran an AM+FM station for 5 or so years not that long ago, 99% of listeners were FM, with very few AM listeners.

How can you possibly measure who’s is receiving your broadcast over the air signal?

The same way you measure everything else about broadcast - you find the people and ask them, aka "surveys".

Are AM listeners and FM listeners likely to find and respond to surveys in the same way? I would expect older more remote AM listeners would be under-represented in your survey.

There's a number of ways to try and avoid response bias - the most obvious would be to (a) work out roughly how many people are listening to AM radio at all, (b) go find some representative sample of people who are listening to AM radio and ask them what they're listening to, (c) scale your results proportionately. Nielsen specialises in this sort of research.

One way is to drive around listening for local oscillator radiation from homes and businesses. That was historically done more for tax enforcement purposes than market research, although I've heard anecdotes about billboards equipped with receivers tuned to survey the radios in passing cars.

Of course, now that chip-scale receivers with synthesized LOs are ubiquitous, intermediate frequencies are no longer limited to 455 kHz and 10.7 MHz, or even used at all. Consequently this method is no longer of much interest, but it worked for the better part of a century.

When you say not working, I think you mean not using. And an unused AM receiver could still be used at some point.

More people listen over DAB than AM or FM now, that threshold was passed in 2018.

I'd speculate that most listening is in the car now. I wonder if any new cars come with AM/FM radios, I'd assume they are all in DAB. In which case it will nearly all be gone in another decade.

The Tesla Model S has an AM radio, though newer Teslas don't:

https://www.soundandvision.com/content/why-tesla-killing-am-...

Supposedly it's more about AM radio being swamped by the RF interference from the car electrics. There was a Tech Guy segment a while back about someone trying to get AM working on their new Tesla:

https://techguylabs.com/episodes/1422/how-can-i-get-am-radio...

I just checked the specs on the 2020 Hyundai models, and they include an AM/FM radio.

Supposedly it's more about AM radio being swamped by the RF interference from the car electrics

I once tried out one of those little BMW electric cars (i3, maybe. The one that looks like it was designed by Ikea), and it didn't have AM radio for that very reason.

It's kind of a big oversight for a car sold in the United States, where the top ten rated radio stations in most large cities includes a number of AM stations.

Currently in New York, the #5 and #12 stations are AM (WINS and WCBS): https://ratings.radio-online.com/cgi-bin/rol.exe/arb001

In Los Angeles, the #2 and #12 stations are AM (KFI and KNX): https://ratings.radio-online.com/content/arb003

In Chicago, the #1 and #3 stations are AM (WBBM and WGN): https://www.robertfeder.com/2020/06/09/chicago-radio-ratings...

Dropping AM radio isn't something that's really happening in civilized countries. For example, in Australia, where the #1 and #8 stations in Melbourne are on AM (3AW, SEN). I wasn't able to find any ratings for radio stations in Tokyo, but when I scan the dial there, I find a good number of AM stations on the air.

Australian here too, and I didn't realise how popular the AM band was until the pandemic. 6PR (3AW sister station) is where politicians were announcing things first, and rival TV & newspapers were quoting 6PR as a source. There's a huge demographic out there I didn't really know about.

My 2018 Skoda came with a dab/fm/am radio. It’s the only radio I have other than an old am/fm radio in a drawer but I don’t think I have batteries for it

The radio I’m listen to In home at the moment is an internet radio using tunein.

In a disaster, local cell towers may not be operational. An AM transmitter located somewhere that is far enough away as to not be suffering from the same local issues could still be operational.

> In a disaster, local cell towers may not be operational. An AM transmitter located somewhere that is far enough away as to not be suffering from the same local issues could still be operational.

Even if the AM transmitter is operational, it is useless to people who lack the ability to receive AM broadcasts.

In Puerto Rico after hurricane Irma and Maria (specially Maria) we didn’t have much in terms of information.

All you need is 1 radio in a community and people can huddle up to listen or just a few listen and take information to others.

Cellphone towers run on generators after disasters with no power and they run out of fuel. People would find and take batteries out of anything they had and give them to whoever had a radio to stay informed. Some people had small solar ones or ones with an internal battery and a crank.

Cellphones became useless quick. No signal and they keep searching for a signal wasting battery quickly and a lot of people had no way to charge them. If the towers came back up and you had battery, they where overloaded quickly and useless.

Simple radios that don't need much infrastructure, such as amateur radio, could be awesome for disaster comms. Unfortunately it seems the hobby is dying, and the bands are under constant attack by the big telecoms who wish to lay their grubby hands on them.

Actually, HAM operators where taken to the island afterward the hurricanes to help the local authorities coordinate.

Here’s an article, https://www.cnn.com/2017/09/27/us/puerto-rico-maria-ham-radi...

Just a guess: if you had any idea how much technological infrastructure has to be intact and working perfectly in order for you to receive an SMS or otherwise use your phone, your opinion would be somewhat different.

A radio requires only two things to be working: the receiver and the transmitter. That's not usually a big deal, but when it is, it is.

My initial training was in aviation ground electronics. I could still design and build a superhet AM receiver from scratch and build from the parts in my workshop here. I am well aware of how immensely complicated the cell-phone system is. Every single component is complicated standing on the shoulders or more complication. QAM is incredible in its versatility and the antennas are so incredible they are works of art. Let alone the routing and higher level protocols. That said, cell systems are designed for redundancy and varying loads. Modern cell towers are spaced so that you can see multiple towers at any one time. They often have power backup and multiple backhauls.

I received a hand cranked emergency flashlight for free somewhere a few years ago. Turns out it also happens to have a simple AM radio built in. It's probably the only working one inside my house, but in a pinch it'll do.

In a pinch my guitar amplifier will do (I don't mean after some soldering, either). AM radios are comically, wonderfully easy to build.

Easy to build by accident, in fact. In retrospect I've no idea how practical physics labs are approved, with the likelihood that some klutzy undergrad (yo) accidentally builds a high-power broadband AM transmitter.

It's not easy to build a high-power narrow-band AM transmitter, let along a broadband one. The issue is the long wavelength makes aerial matching difficult (at 1MHz the wavelength is 300 metres, i.e. speed of light/frequency). AM transmitters for national use generally run 10's to 100's of kilowatts of power [0], and longwave is even higher, e.g. UK Radio 4 is 500 kilowatts.

Pretty unlikely to build a high-power one by accident :)

[0] http://www.mediumwaveradio.com/uk.php

Preparing AM/FM radio as well as food and water for disaster is commonly recommended here in Japan. Smartphones are more useful but cellular tower could be down due to power or connectivity issue. (occurred on 2019 typhoon event in Chiba and NOW occurring in Kumamoto)

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