How to Make a Crystal Radio – No Batteries, No External Power (2015) [video] | Hacker News Reader

How to Make a Crystal Radio – No Batteries, No External Power (2015) [video]

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94 pointshumbfool223 comments

For Crystal Radio Lover:

Foxhole radio (https://en.wikipedia.org/wiki/Foxhole_radio)

How to Make a Foxhole Radio: https://www.youtube.com/watch?v=skKmwT0EccE

I read about, but never tried, an even more primitive diode for this: Burn sulfur on the end of a fine copper wire, then touch it to a piece of lead. Seems like you could do something with iron pyrite, too, but I can't remember the details. I'm sure they came up with a ton of these in the early 20th century that never made it into mass production.

Edit: https://books.google.com/books?id=S1QyAQAAMAAJ&pg=PA46&lpg=P...

Unfortunately it seems like you need a power source to initially condition the rectifier, which you might not have in a WWII foxhole.

A plain copper oxide to copper Junction makes a serviceable diode for a crystal set.

Interestingly this is the main thing to watch out for with speaker wires - not the cable, it is the junctions that matter by far.

burning sulfur on a chunk of copper will also make you a memristor. interesting effect...

Thanks. very interesting, I'm gonna to make a memristor!

https://news.ycombinator.com/item?id=9853984

I’ve been wondering how to do that for years! Thanks!

Electronics learning kits from the 60's-90's had this, maybe they still do. Crystal earpiece, adjustable ferrite coil or variable capacitor, piece of wire as an antenna and ground to metal drainpipe. No batteries needed as the power was taken from the station's broadcast.

I don't know if they have anything quite like those old Radio Shack 100-in-1 electronics kits any more. I've wanted to get something like that for my nephews and couldn't find it.

They do: https://www.robotshop.com/en/elenco-mx-907-200-in-1-electron...

The various snap circuits kits is probably the most popular modern replacement.

https://www.elenco.com/brand/snap-circuits/

I really liked those kits. I didn't understand digital logic or analog circuits back then but tinkering and getting the satisfaction of building something is what eventually led to my career in engineering.

I saw this recently- a guy built an AM radio with a 555 timer. https://youtu.be/YC72J2VOSH0

It is very simple to build a 555 radio. back in 2011-2012, Eric Schlaepfer had built it.

...Yes, the guy in the video is Eric.

For the enthusiasts:

https://www.midnightscience.net/home.html

http://www.neodux.com/read/Worlds_Simplest_Radio

This is very impressive

TL;DW guy builds a passive AM diode receiver; hand-wound inductor.

This is pretty much the first receiver topology that EE undergrads who take a first course in comm systems analyze in any detail. It's also a fun way to get a kid interested in electronics.

Yeah, I made and listened to a crystal radio as a kid in Britain. With a big antenna hung outside between trees I could listen in bed to Radio Luxemburg! (this was in the days when the BBC was the only broadcaster in Britain; Radio Luxemburg let me listen to the pop music the Beeb didn't play).

And yes, later I went to an EE course at uni!

It's also kinda fun to use them to sniff your various electronic devices. I remember holding one up to my old Amiga 500 and listening to the emissions it was producing.

My home-brew Z-80 system, with dozens of unterminated copper traces wiggling rail-to-rail square waves at 5 volts in an unshielded cabinet, wiped out TV reception with herringbone patterns for a couple houses around. It was the 1970s, nobody knew it was me, practically nobody had computers at home or the knowledge of electronics to make the connection.

Ironically I could turn it on today and no one would notice (unless it totally wiped out wifi, which seems unlikely).

Maybe wireless car keys. People would notice they are jammed, one time it did happen to me and neighbors. But I think the perpetrator was not caught.

Also, FM/AM radio is still widely used.

> FM/AM radio is still widely used.

But not nearly as wide as it used to be. The bands from LW all the way to 108MHz were absolutely crammed with stations. I got one of my sons a second hand world radio set and it is actually pretty barren on most wavelengths.

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