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Emergency Crystal Radio

A simple radio for emergencies that needs no power
  (+19, -2)(+19, -2)
(+19, -2)
  [vote for,

During an emergency, be it a natural disaster, refugee crisis, whatever, getting information to the people is one of the most important but difficult tasks, my idea is a cheap, easily distributed radio that needs no batteries, a crystal radio. Basicly the radio would be a plastic box with 1 knob (tuning), one earphone, and one coil of wire for an antenna. These could be distributed by soldiers, emergency personal or even airdroped (like food packets), simple graphic instructions (pictures) cold be printed on the radios to show people how to use them and they could tune in instructions on the radios.
Hirudinea, Jun 11 2009

1N34A germanium diode http://www.datashee...crosemi/MSC0955.pdf
10^6 hour MTBF [csea, Jun 12 2009]

Crystal television http://www.homecine...th+Swarovski+LCD+TV
Inspired by [zen_tom] [coprocephalous, Jun 12 2009]

Crystal mobile phone http://www.vertu.co..._ascent-ti_sapphire
[coprocephalous, Jun 12 2009]

Crystal Blue Persuasion http://www.youtube....watch?v=LN38vED24Eg
[normzone, Jun 12 2009]

Fractal antenna http://www.fractenna.com/
Looks pretty spiral to me [nineteenthly, Jan 27 2011]

Crystal cell http://laserhacker.com/?p=326
crystal cell made using copper magnesium and epsom salt and borax with some potassium chloride in equal parts. [travbm, Dec 11 2015]

FM crystal radio http://solomonsmusi...M_CrystalRadio.html
A radio with a smaller inductor coil may be idealy powered by crystal battery. [travbm, Dec 11 2015]


       21 Quest Google "Crystal Radio", as for the hand cranked radios they're to expensive, goverments wouldn't pay for it, and solar dosn't work at night, crystal seemed the cheapest no battery radio.
Hirudinea, Jun 11 2009

       Were all those refugees signed up to a 12 or 18 month contract?
Ian Tindale, Jun 11 2009

       //Now, my first question about your idea is this: how does it work without power?// Powered by radio waves.
coprocephalous, Jun 11 2009

       I used to build crystal sets when I was very young. It's what got me into electronics later. Dead simple - a longwire aerial, an earth connection, a tuned circuit consisting of a hand- wound coil and variable capacitor, a detector consisting of a germanium diode, and the output goes into a crystal earpiece. That's it - there's enough power to drive the earpiece from that.   

       It's frequently observed as typical of the americans mentality to strive for as high a technology or most impressive fire-power as possible in their solutions to problems. The support infrastructure of mobile phones is complex and high-tech, and the devices themselves are beyond individual understanding and can't be created or fixed by real people.
Ian Tindale, Jun 11 2009

       Well, when I was a youngster I wasn't the only one building crystal sets. I think most of my generation were doing something practical, something directly connected to a person's understanding, which people are returning to now after a few decades of highly abstract equipment full of who knows what, with functionality designed by random engineers embodying their guess as to what you need and how to achieve it. It's coming back to reality.
Ian Tindale, Jun 11 2009

       I still have a working crystal set from when I was young. Crystal radios are so cheap that every 'normal' radio ought also to contain a backup crystal radio. There would just be two extra terminals on the back - one should be connected to Earth (or your copper central heating pipes) and the other should be connected to a long bit of wire hanging out of your window.
hippo, Jun 11 2009

       Having an emergency crystal radio set sounds like a good idea, especially if they could be set to a standard frequency. Having a broadcast system too so people could try to contact others with emergency crystal sets if central organisation has been completely wiped out would be good too.   

       Great for zombie apocalpses.
Aristotle, Jun 11 2009

       // Crystal radios are so cheap that every 'normal' radio ought also to contain a backup crystal radio//
I look forward to the crystal DAB radio.
coprocephalous, Jun 11 2009

       //It's frequently observed as typical [...] to strive for as high a technology or most impressive fire-power as possible in their solutions to problems.//   

       Hmm, sounds pretty typical of the 'Bakery...
csea, Jun 11 2009

       21Q you have made an ass of yourself.
WcW, Jun 11 2009

       How well can crystal sets be made to work in areas with many powerful radio stations? Is there any practical way to get sufficiently-selective tuning without using a tuned-oscillator (superheterodyne or homodyne) receiver?   

       BTW, at the London Science Museum, I saw a wind-up radio in which the audio transducer would vary the down pressure on a bead that was riding on a disk. This bead was connected via string to a diaphragm. As the disk turned, friction with the bead would pull the string; varying the pressure on the bead would vary the tension on the string. Supposedly, this allowed a small electric signal to produce a larger amount of sound energy. I have no idea how well it actually worked.
supercat, Jun 11 2009

       I got to bun anything that brings back interest in crystal radio.
tatterdemalion, Jun 11 2009

       Makes sense (+), the cell phone alternative is usually useless as the service is out because the towers loose power. For hurricanes, they might want to re-aim the Voice of America transmitter for emergency broadcast use.
MisterQED, Jun 11 2009

       Yes, really nice idea. Luddite that i am (who has two DAB radios and a variety of remarkably un-Ludditey things such as this very device), i actually think we should just scrap the whole system, including telly, and just have crystal sets. Presumably they don't do FM? Fine by me!
nineteenthly, Jun 11 2009

       21 Quest, the author describes the idea clearly - a cheap crystal radio designed to be distributed in emergency situations. It seems like you are struggling to find a reason to dislike the idea. I don't understand why you do that. Why don't you endeavour to find reasons to like ideas?   

       nineteenthly, I seem to recall reading something about FM on crystal radio, so that might be possible but I imagine signal strength issues would defeat this purpose.
tatterdemalion, Jun 11 2009

       It's not the signal strength, it's that there's no simple way of detecting the frequency modulation signal of the carrier in the same way that it is very easy to detect the amplitude modulation signal of a carrier in an AM transmission.   

       If you imagine that its easier to create a circuit design that looks for a "there's more signal now, oh wait, its coming back down to the original signal level now, oh wait, there's less signal level now, ah, its going back up to the orig…" change in the carrier signal than it is to create a circuit design that works on a "the frequency has shifted up to a higher frequency, oh wait, its coming back down to the original frequency, oh wait, its transmitting at a slightly lower frequency now" kind of detection. In each case, the detected change (ie, the modulation) becomes (well, is) the actual audio signal.
Ian Tindale, Jun 11 2009

       I don't have a crystal set around right at the moment, but I'd be downright embarrassed if I couldn't put one together in a few minutes from stuff I can find around here. (Not going to try it right now, because it would probably mean sacrificing some working power supply to nip a diode out of it, but knowing where it is and how is something worth remembering occasionally.)   

       I haven't actually put one together for quite some years now, and not since they started using that AM stereo style broadcasting - anyone have any experience with that & crystal sets?
lurch, Jun 11 2009

       //variable capacitor, a detector consisting of a germanium diode// Aww, that's hi-tech. Piece of coal and very fine wire for a real crystal (hence the name) set.
MaxwellBuchanan, Jun 11 2009

       Coal? Never tried that, and got plenty of it around, so I may just have to. I've used lead crystal, and a cat's whisker. And at the moment, there is a cat about, unaware of the danger...
lurch, Jun 11 2009

       No [bigsleep], no, i want wireless internet on crystal set receivers. I don't know what to do about the uploading bit though. I believe in packet radio internet using crystals, and maybe valve-based things which aren't modems too. I want the room i'm halfbaking in to be lit by the warm red glow of the thermionic valves in my belljar-encased modem and filled with the clattering sound of the teleprinter as i feed in my ideas on punchcards. Incidentally, the download bit is still by crystal set in this scenario and only the uploading involves those new-fangled valve thingies. Actually no, having looked on Wikipedia, i see that a spark gap transmitter makes more sense.
nineteenthly, Jun 11 2009

       //Coal? Never tried that// Actually, to be frank, nor have I. But I understand that it used to be the common way to make a crystal set. Presumably, the coal has a crystalline structure that can do whatever the crystally thing is that it needs to do. Rectification, that'd be it.
MaxwellBuchanan, Jun 11 2009

       Yes, it's a combination of the coal itself, and the fine point of the end of a wire touching a certain 'good' part of the coal, that forms a junction, and acts a bit like a diode.   

       One avenue of research is to look up the types and sophistication of the various radios built by POWs in wartime captivity from whatever they could scrounge - it's quite interesting how much they could put together, and how discreet it had to be.
Ian Tindale, Jun 11 2009

       Coming Soon - the Crystal Meth Set - so you can get up with the boys before getting down with the boys and then getting up again (and down later)
gnomethang, Jun 11 2009

       //Piece of coal and very fine wire//
Was it really coal?
I remember it as being coke. (the stuff that's left after making town gas, not the drink or the white powder)
coprocephalous, Jun 12 2009

       I use a piece of crystal as an under arm deodorant. (where I come from we call this area of the anatomy The Oxters) I often wondered why I could hear the faint tones of R4 news as I leaned over the sink in the morning.
xenzag, Jun 12 2009

       When I was young (back in the day) I had the Reader's Digest Omnibus for Children. It had some excellent plans for building a crystal set that I was going to build. I probably would have got around to it were it not for the fact that I could receive Laser558 using my father's JVC Music Centre.
wagster, Jun 12 2009

       //back in the day//
There was also a Ladybird book, showing how to build a crystal radio.
coprocephalous, Jun 12 2009

       [Bigsleep], i think it might depend on what you mean by "better". I know nothing right this second, but efficiency and amplification are not the only issues. There's also robustness, ecological impact and ease of construction from bits lying around by someone with relatively little talent and skill, and the unavailability of the likes of vacuum pumps and clean rooms. I can see that photovoltaic cells provide a fair amount of umpf for radios, but silicon needs to be kept sealed away from oxygen and water. Other than that, i can imagine solar power working on parabolic mirrors heating water for a steam turbine or perhaps thermocouples, but otherwise it seems to me that there's too much dependence on some kind of infrastructure. I don't know how to compare a crystal set with a photocell-powered tranny (not me, the radio) on that basis.
I'm not saying it isn't better, just that i don't know.
nineteenthly, Jun 12 2009

       //Crystal sets are notoriously unreliable.//   

       Cat's whisker type crystal sets, maybe. 'Modern' = 1950's era germanium diodes tend to be very reliable (q.v. [link] = 1 million hours MTBF.)
csea, Jun 12 2009

       It wouldn't be long before someone created a "bling" version where the crystal is one of those Swarovski glass beads, and all the wires are solid gold...
zen_tom, Jun 12 2009

       Germanium has a lower forward volt drop than Silicon, which I suppose would make it more sensitive. I don't happen to know if there are better diodes. Maybe the cat's whisker technique is better?
Mind you, two small pieces of zinc and copper, or something like that (two coins?), and a nice cup of salty water might be enough to power any small, well designed, radio.
Ling, Jun 12 2009

       //Crystal sets are notoriously unreliable//
So are solar-powered radios at night-time.
coprocephalous, Jun 12 2009

       I've found that solar-powered radios last all night with an earphone, so i don't think so, given the weedy sunlight at this latitude. Also, there are even batteries which run on tap water and generate enough power for an LCD clock at least.
nineteenthly, Jun 12 2009

       Definite [+] from me. Mass produced on a single PCB, with an integrated piezo speaker, factory tuned to a single emergency frequency. Case or shrinkwrap optional. Should be about 10c apiece, including the antenna wire, and the size of a matchbook. The piezo is so more than one person can listen at a time. If it's too quiet, hold it up to your ear.
BunsenHoneydew, Jun 12 2009

       /I'd be downright embarrassed if I couldn't put one together in a few minutes from stuff I can find around here./   

       I like this. I want video. It would be a series called "Building the Crystal Radio". McGyver soundtrack. I want to see lurch appeared in various locales with his swiss army knife and given carte blanche to disassemble anything within 100 yards to make his radio. I want to hear the tinny tunes of AM radio closing each episode and see lurch nodding in time with the thing to his ear.
bungston, Jun 12 2009

       I think i've suggested this before and it's probably impossible, but i want video too, on a tiny magnified LCD screen, on the actual crystal set. Is that completely impossible? I envisage a microscopic LCD viewed through a microscope.
nineteenthly, Jun 12 2009

       Not completely impossible. Watch for the description shortly, in the form of a new idea. It won't be quite what you're after, but I think it might be interesting anyway.
lurch, Jun 12 2009

       // and one coil of wire for an antenna. //   

       I am not sure if thatwill work. Unless coil is uncoiled into making a long antenna.
VJW, Jan 27 2011

       There are fractal antennae and i'm pretty sure i've seen old crystal radio projects using spiral ones.
nineteenthly, Jan 27 2011

       [VJW] the coil works; I built one when I was a kid; it's how you tune it: run the wire across the coil to get different frequencies... saves you running up and down a few 10's of feet of wire.   

       I don't see any reason you couldn't have a modem on it for digital... wait, can you transmit on these things ?
FlyingToaster, Jan 27 2011

       They use power from the radio waves themselves, so i'd expect there to be a few snags.
nineteenthly, Jan 27 2011

       A masterly understatement as ever, [19thly].   


       O-Kay .... after a bit more thought ....   

       It is possible to "harvest" small amounts of RF energy, if you're sufficently close to (for instance) a high power AM (or indeed Radar) transmitter, and you have a large antenna of the correct size. Indeed, if you can edge into the Near Field (a kilometre or so, for a 200 kHz AM transmitter like BBC Radio 4 Long Wave), you're probably going to be able to get power in the order of Watts with not a lot of effort or equipment.   

       That would, with sufficentrly low-power electronics and a decently efficent RF PA coupled to a well designed half-wave dipole tuned to a good VSWR, allow you to transmit 3.6 kHz audo over a range of tens of kilometres, if you were high enough above terrain, given a sufficently sensetive receiver.   

       So it could be done.
8th of 7, Jan 27 2011

       //Maybe not governments, but let me tell you something about the USA...(all the rest)//   

       So you work in the cellular industry...and you are unaware that cellular, this "Vastly more reliable" technology, is nearly useless during and for a period after disasters or consumer electronics shows?
KAGE, Jan 28 2011

       Just come across this one again - I think the alternative crystal was coke (no, neither the soft drink nor the hard drug), not coal.
coprocephalous, Jan 31 2011

       Thanks [ of ], so that gets it from the Freeman's Common radio mast to about Filbert Street and the junction with Upperton Road, which is still not close enough, depending on the power of the radio mast i have in mind.
nineteenthly, Jan 31 2011

       Yes. And you can forget about portability ...
8th of 7, Jan 31 2011

       //Katrina ... We take care of our own//   

       Ha ha ha ha ha ha. Wait, you're not serious, are you?
nomocrow, Jan 31 2011

       Kids build potato (and other fruit/veg) batteries in early science projects. Can adults make emergency radio devices powered by them?
cudgel, Jan 31 2011

       My potato battery ran a light emitting diode.
travbm, Oct 29 2015

       You can make crystal radios where power comes from the signal. It is possible to make a FM band crystal radio but selectivity may be low. Although solar panels do not work at night. I have made a solar radio using a solar panel and batteries out of an old cordless phone that will play at least all night long. But if you do not want to use that you may try a crystal battery to power the thing from laser hacker.com. I had thought of making a crystal battery using magnesium and copper strips with rochelle salt and zinc oxide to make the diode crystal, the magnesium is the positive junction of the diode. So It may put in parallel with radio diode with the output going to the other side of the speaker with the radio diode connected to the other end of the speaker to get more power going to it. Also for crystal FM radio you may try a 1N5711 diode. A crystal battery may power the speaker or put an activating voltage on the diode.
travbm, Dec 11 2015

       Ah, and here's yet another opportunity to speak in defense of poor [21Quest], who's annos were cruelly deleted from many ideas by alien invaders.   

       So, from memory, I believe the point that [21] was trying to make above, was that he was welcoming all halfbakers to descend on his domicile and build crystal radios simultaneously in an effort to set a Guiness world record for most obsoleted technology functioning at one moment. I'm sure he'll be by shortly to give us the address.   

       I remember crystal sets - they were an oddity in the sixties, but always amazing to demonstrate old school tech to a kid.
normzone, Dec 11 2015

       These days you can achieve the same effect by showing them a cellphone with a monochrome LCD display and a physical keypad instead of a touchscreen.   

       They'll probably ask where you pour the whale-oil in and where the wick is ...
8th of 7, Dec 11 2015

       Ha !   

       THAT'S Version I.   

       The Mark II not only ferments sugary carbonated beverages and distills them to fuel itself, but there's a separate overflow container option.
normzone, Dec 11 2015


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