h a l f b a k e r yClearly this is a metaphor for something.
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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.
This one uses a pullstring...
http://www.ambientw...m/lilgyoamandw.html
...and it also has a flashlight, cellphone charger, headphone port, and am/fm/weatherband radio. [21 Quest, Jun 10 2009]
Handcrank, solar *and* battery powered
http://www.ambientw...m/kakahacrsoac.html
[21 Quest, Jun 10 2009]
Here's one you can make yourself. No power!
http://www.wimp.com/radiofun/
[21 Quest, Jun 10 2009]
FM Crystal set
http://www.somerset...m_crystal_set_1.jpg
[bigsleep, Jun 11 2009]
Cat's Whisker (picture of)
http://en.wikipedia...ristalldetektor.png
Back in the days when electronics was partly mechanical and well before it got virtual and then quantum. [bigsleep, 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]
[link]
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Dude... that's what hand-crank emergency radios are for. And they're pretty cheap, too. In many places that have frequent natural disasters, commodities that are considered emergency or survival equipment, such as generators, flashlights, radios, and batteries, are exempted from sales tax to ensure that they are as affordable as possible. |
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Now, my first question about your idea is this: how does it work without power? |
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My second: Do such radios already exist, or have they ever existed, to your knowledge? |
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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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Maybe not governments, but let me tell you something about the USA. During Huricane Katrina, several telecommunications companies actually gave out cellphones for free to hundreds of thousands of refugees. There's no need for governments to shell out a dime for this. We take care of our own. Better to have *slightly* more expensive but vastly more reliable equipment than cheaply made junk that can't be counted on. |
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Were all those refugees signed up to a 12 or 18 month
contract? |
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Neither. They were prepaid phones, and AT&T offered over 100
free minutes with each one they gave out. |
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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 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. |
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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. |
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You think most people could figure out how to build or repair a
radio? Most people these days don't even know what a radio
*is* outside a car or alarm clock. I'd wager most folks would be
looking for the batteries, myself included. I mean, I get it now.
But most people aren't very tech savvy. |
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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. |
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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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Well my other question seems to have been answered. Clearly
these exist. So what's the idea? Mass distribution? Sounds more
like advocacy than an idea. But hey, that's just my opinion... |
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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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//i actually think we should just scrap the whole system// |
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What !? What !? Including the internet and the HB ? |
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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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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. |
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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. |
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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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<virtually looking back>Coal! How decadent !</vlb> |
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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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// as i feed in my ideas on punchcards.// |
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Which are no doubt cleverly disguised usb sticks. Gotcha. Faux nostolgia stuff, like the knitting machine that looks like a loom but can still download patterns from t' 'net. |
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This idea also suffers from a similar problem. It would be possible to make a better no-power radio with modern technology. Possibly one with a full tuner and a solar cell that could power a piezo speaker when sunlight is available (but I guess that is implied in the idea as crystal radio is only really mentioned in passing). |
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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. |
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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. |
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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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The idea is specifically to air drop large number of cheap, simple radios during the emergencies mentioned. This implies mass production of some kind and we're all geared up to make robust solar powered radios the size of a usb stick. I guessing the unit cost would be under $1. Crystal sets are notoriously unreliable. |
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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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[csea] I was saying that in response to dependence on infrastructure and clean rooms. If you're using a mass produced diode, you might as well use modern custom integrated circuits. I think we're also overlooking the ease of making a crystal ear-piece. Maybe the vocal chords of a local animal could be modulated by inserting electrodes ? |
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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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