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Comment by kpgraham | Hacker News Reader

It used to be possible to make a radio receiver out of a diaper pin and a blue razor blade. The coating on the blade acted like a crystal. You needed a cheap pair of headphones or a tiny transistor radio speaker. I made one when I was a kid, and I could clearly pick up 77 ABC in New York City from 50 miles away. Razor blades aren't blue anymore, but there must be other things that work.

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Fun fact, the blueing that creates that effect is literally just steel blue. You can accomplish the same thing by torching a razor blade until it glows then letting it cool.

A bit like this: https://blog.jgc.org/2012/02/my-foxhole-radio.html

It still is, and I hope it remains that way for future generations too.

The first-time experience of hearing "voices from thin air" is unforgettable.

Did you do this before you ever used a full on radio? That seems hard to believe, so I guess you are implying that it is an experience that feels different. I wonder how so?

Consumer radios operate by witchcraft. Presumably a fairy from another dimension rides into town on horseback with a satchel full of vinyl and then camps out outside your window so when she sees you switch on the radio she can play the vinyl for you.

It feels different when you put it together yourself out of basic components and see that there is no magic in there, and yet... there is.

On a serious note, it concerns me a little how easy new generations accept that everything is a magical black box and not even question how their smartphones work.

Isn’t it interesting that the more technology people have, the less they understand how it works?

The profit motive for business is to make things easier to use, but ironically that also makes it less likely for anyone using it to have any idea how it actually works. The reason most of us are here is because we had to struggle and learn in order to get computers to work. I don’t think as many kids today will have that opportunity, which probably means that we’ll have more people who use technology but less of them capable of creating it.

This is true, but those kids will simply operate at a higher level of abstraction than we do and get bigger things done. I don't know how to fab a transistor, but I can make good things happen across billions of them.

You need to plug in or put batteries in a regular radio, but a crystal radio has no apparent power source of its own.

> blue razor blade

I first ran across the designs for these radios in a corner of the Old Web on a site called Bizarre Stuff You Can Name In Your Kitchen:

<http://web.archive.org/web/20040918174026/http://www.bizarre...>

Coming back to correct this obvious typo so that site search (and outside crawlers) will pick it up. The correct name is: Bizarre Stuff You Can Make In Your Kitchen.

It's a shame a lot of Europe is either killing off its AM output or already has which will render this impossible, the last transmitters other than a couple of low-power enthusiast stations including the venerable BBC Radio 4 longwave are being shut down over the next couple of years.

Definitely reckon Ofcom should open the band up to hobbyists given it's not much good for anything else.

DRM can be useful. Unfortunately hard to google because of the other DRM. https://en.wikipedia.org/wiki/Digital_Radio_Mondiale

136KHz is available : https://rsgb.services/public/bandplans/#5

and 472KHz (https://rsgb.services/public/bandplans/6/)

and 1.8-2Mhz (https://rsgb.services/public/bandplans/7/)

There a surprising amount of things it can be used for and some really interesting innovation at the bottom end of the spectrum. Well worth getting qualified as an Amateur operator if you want to experiment.

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