
How to Make a Crystal Radio – No Batteries, No External Power (2015) [video] - humbfool2
https://www.youtube.com/watch?v=8XR9Uzy2RPM
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MrXOR
For Crystal Radio Lover:

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

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

~~~
13of40
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...](https://books.google.com/books?id=S1QyAQAAMAAJ&pg=PA46&lpg=PA46&dq=copper+wire+sulfur+lead+rectifier&source=bl&ots=VTJNHvvCGm&sig=roNipTzMhsT-
Fv3o5HrtNN_IFF8&hl=en&sa=X&ved=2ahUKEwjR6s7-hsnfAhWn64MKHePDDi4Q6AEwD3oECAQQAQ#v=onepage&q=copper%20wire%20sulfur%20lead%20rectifier&f=false)

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

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

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

[https://news.ycombinator.com/item?id=9853984](https://news.ycombinator.com/item?id=9853984)

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heyjudy
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.

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dhosek
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.

~~~
dylan604
They do: [https://www.robotshop.com/en/elenco-
mx-907-200-in-1-electron...](https://www.robotshop.com/en/elenco-
mx-907-200-in-1-electronic-project-lab-
kit.html?gclid=EAIaIQobChMIgdLYuJnJ3wIVi7bACh30wAXNEAQYAyABEgKiKPD_BwE)

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

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

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

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JoeDaDude
For the enthusiasts:

[https://www.midnightscience.net/home.html](https://www.midnightscience.net/home.html)

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grendelt
[http://www.neodux.com/read/Worlds_Simplest_Radio](http://www.neodux.com/read/Worlds_Simplest_Radio)

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smithmayowa
This is very impressive

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metaphor
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.

~~~
01100011
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.

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kabdib
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).

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rini17
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.

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jacquesm
> 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.

