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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.
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]
[link]
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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. |
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//Now, my first question about your idea is this: how does it work without power?// Powered by radio waves. |
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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. |
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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. |
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Great for zombie apocalpses. |
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// 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. |
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//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.// |
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Hmm, sounds pretty typical of the 'Bakery... |
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21Q you have made an ass of yourself. |
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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? |
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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. |
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I got to bun anything that brings back interest in crystal radio. |
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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. |
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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! |
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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? |
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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. |
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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.) |
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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? |
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//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. |
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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... |
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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. |
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//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. |
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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) |
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//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) |
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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. |
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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. |
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//back in the day//
There was also a Ladybird book, showing how to build a crystal radio. |
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[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. |
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//Crystal sets are notoriously unreliable.// |
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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.) |
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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... |
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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. |
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//Crystal sets are notoriously unreliable//
So are solar-powered radios at night-time. |
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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. |
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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. |
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/I'd be downright embarrassed if I couldn't put one together in a few minutes from stuff I can find around here./ |
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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. |
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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. |
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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. |
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// and one coil of wire for an antenna. // |
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I am not sure if thatwill work. Unless coil is uncoiled into making a long antenna. |
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There are fractal antennae and i'm pretty sure i've seen old crystal radio projects using spiral ones. |
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[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. |
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I don't see any reason you couldn't have a modem on it for digital... wait, can you transmit on these things ? |
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They use power from the radio waves themselves, so i'd expect there to be a few snags. |
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A masterly understatement as ever, [19thly]. |
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O-Kay .... after a bit more thought .... |
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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. |
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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. |
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//Maybe not governments, but let me tell you something about the USA...(all the rest)// |
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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? |
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Just come across this one again - I think the alternative crystal was coke (no, neither the soft drink nor the hard drug), not coal. |
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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. |
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Yes. And you can forget about portability ... |
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//Katrina ... We take care of our own// |
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Ha ha ha ha ha ha. Wait, you're not serious, are you? |
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Kids build potato (and other fruit/veg) batteries in early science projects. Can adults make emergency radio devices powered by them? |
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My potato battery ran a light emitting diode. |
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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. |
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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. |
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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. |
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I remember crystal sets - they were an oddity in the sixties, but always amazing to demonstrate old school tech to a kid. |
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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. |
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They'll probably ask where you pour the whale-oil in and where the wick is ... |
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The Mark II not only ferments sugary carbonated beverages and distills them to fuel itself, but there's a separate overflow container option. |
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