How to: Make a simple Crystal Radio

I know there is many on this topc but this is slightly different. Instead of using magnet wire, gelana, iron pyrite, germanium diodes, I have used a rusty knife blade (A craft knife with the snap of blades) and a pencil lead as a detector, a crystal Earphone as an earphone, Solid Cat 6 wire as the winding wire for the coil, hookup wire as an aerial and earth. Hope this shows you that you really can use anything to make this work. Im sorry for the lack of pictures in constuction (Im doing this in retrospective to start with)

Step 1 Matarials

This may end up as a running list as I improve/modify the radio.

For the Coil:
4 meters solid core Cat. 6 wire (4 twisted pairs)
3" OD PVC pipe

For the Cat's Whisker Detector:
1 old rust craft blade
1 HB (expierement) pencil
Hook-Up wire
1 paperclip
Small Piece of wood (to mount on)
3 wood screws (preferably cap but if you want to use counter sunk then you need custom metal washers too.)

Misc Electrical:
LOTS of hook-up wire (I bought 25 meters and turned out that was only just enough)
Variable Capacitor (Mine was 60pf - 160pf)
Crystal Earphone (normal MP3 headphones won't work apparently but feel free to try them out)
Germanium Diode (for testing although not necessary)
Aligator Clips

Tools I used:
Hammer
Nail
Cordless Screwdriver
Number 8 wire (I think in america it might be called fencing wire otherwise google it)
My Sisters electronic board (I needed a Germanium Diode and a tuning capacitor. I no longer need the Germanium Diode and im buying a variable capacitor)
Soldering Iron
Solder (I guess you could call it a tool. Maybe if you considder it as an adhesive)
Automatic Wire Stripper (This is AMAZING!! If you dont have one then you need it. I strips wires and can cut them to. Saves me hours!!)

Comments

[sonamsnv]

It’s very useful article thanks for the sharing the good and informative information .Thank u….
Fence Company

[moparman]

A fast and easy way to untwist CAT5, CAT6, etc. wire is to tie one end of the twisted pair to something solid and put the other end in a drill chuck. Keep the wire tight as you run the drill and in no time at all you'll have the individual wires separated.

Gene

[LasVegas]

Your schematic is way too complex for a foxhole radio. You've already constructed about all you need for it. A 120 wind coil and a razorblade/pencil diode. Adjusting the position of the pencil lead is how the unit is tuned. That along with a sensitive enough earphone, a good ground (water pipe) and arial and you're ready. The radio you've drawn is a crystal set, but wouldn't qualify as a "Foxhole radio" since it requires parts that a solder wouldn't have had in the field.

[riverreaper]

i bet if i was in a foxhole a pencil could just wright a not an a simple few folds i could fly it to the guy next to me an so forth passing the note over quicker that shakeing hands could build any of that in hope the main radio guy was lissening an if so didnt think i was the enimey try a fast on then ordering a bombing onto me lol ~the british are comeing the british are come say do u have extra news print ive to poop now ~

[Phil B]

Foxhole radios allowed soldiers to keep up on news about the progress of the war. I read an article about POW's in German camps listening to the BBC to get news. Such news was a counter measure to propaganda prison camp officials might want to use to control the morale and thoughts of the prisoners. Even the German guards were not getting reliable news about where the front was and how close the Russians were. Although guards were to confiscate contraband, like radios, one guard knew about the prisoner's radio and sought out the prisoners to get good information he could not get elsewhere. When the prisoners went out on work details they stole telephone receivers and bicycle generators to get wire for radio coils. They picked up chunks of coal slag from furnaces that had been used on roads like gravel and made radio detectors from sensitive points on the slag pieces. At night power was cut to the barracks and soldier connected their radios to the electrical system to use its wire for an antenna. Many of the prisoners had experimented with crystal radios as boys before the war.

[microman171]

I don't think you understand the concept of a foxhole radio at all. It is a receiving device, and the soldiers would use it to listen to the news about the war. With a fox hole radio, soldiers could listen to victories from other units, tragedy back in England, or even just listen to music. Morale was a very important thing to keep high in the war.

[n0ukf]

The pencil "lead" isn't what tunes the radio, it's what detects (demodulates) the audio out of the RF signal. The coil and capacitor make up a tuned circuit which when adjusted (amount of plate meshing and coil tap positions) tunes in the desired station. You can make a capacitor by using a couple foiled gum wrappers (or some foil and paper) and rolling your own, making sure the two foil "plates" don't contact each other to short it out.

[microman171]

So all your saying is if I remove the capacitor then I could call it a fox hole radio?? A lot of the soldiers pulled apart motors and radio gear to get the headphones and winding wire. Maybe the soldier got the variable cap out of the radio?? This coild is an 80 wind coil. I dont know how you can get different stations witht eh pencil though.

[LasVegas]

Yes. Remove the capacitor and the switch. Yes. Soldiers built all sorts of radios using all sorts of parts, but the device that became known as the Foxhole Radio was build with what they had on hand and didn't include any components other than the unusual crystal made up of the pencil and razer blade. They were "Blue Blades" at the time, made from galvanized steel. It was tuned by moving the lead around to find just the right spot on the blade that filtered a station through.

Here is a good example of a Foxhole Radio.

[microman171]

O yes I see. I have changed the name to a simple crystl radio. Thanks for pointing it out :D

[LasVegas]

I would have liked to see you complete the Foxhole Radio! You were well on your way. All you need are a few more windings and a 300 ohm earphone. I'm sure that knife blade would work well.

[microman171]

Im thinking of makeing many more adios so that could b on the list. I dont have tubes but apparently you can make them

[the "wow shammy"]

i have c quick question, can i use a normal speaker instead of the crystal ear phone? thanks

[Phil B]

I see you did not get an answer to your question. A crystal radio has no added source of power--only the energy in the broadcast signal. A normal speaker requires additional power from an amplifier with an added power source, like a battery or power from a wall socket. An earpiece needs much less power than a normal speaker and can make enough sound to be barely heard. Some circuits use a crystal radio circuit to detect and tune the signal. Then they add a small amplifier circuit to drive a normal speaker.

[FeedTheGrid]

Very cool.

[Xellers]

Where could I get a crystal earphone without buying one. Is there anything I can take one out of? Would an old telephone headset work?

[microman171]

What country are you from? Most earphones/headphones dont use crystals ear pieces anymore.

[Xellers]

My base is in the US of A right now. But I do have access to some very nice "old stuff" that isn't really antique, but is more like '70s and '80s era.

[microman171]

I wouldnt think it would be that hard to find one in USA. Im not sure about old equiptment. Maybe you can get one out of a toy?

[Xellers]

I just dug up this old telephone that has a spinning dial. Do you think that the headset from that would work? I can just unplug it from the main unit, and put a new cable into it as not to harm it.

[microman171]

I'm not sure, I still think it would be a peizo. Just buy one... I live in New Zealand and this kind of thing is VERY hard to get, but I managed for about $2.

[Xellers]

I took apart the telephone and found out that it was in fact a peizo. Unfortunately, it wasn't sensitive enough for me because I couldn't pick anything up with the radio I built. I simply can't put up a hundred foot antenna... I'll have to wait to get a super high impedance crystal earbud...

[sousa]

Hello, I think you don't have to wait any more. Just mesure de piezo resistance and manage one resistor that, connected in parallel to the piezo, give out one resistance of about 2k ohms. I use 1Meg resitor and it works. Or else get one audio tranformer (impedance tranformer) and connect the your radio to the primary(about 2k ohms) and the piezo to the secondary(about 15k ohms). You can also use an ordinary 9v-220v transformer. It works, but it's not so efficient as the audio T. Note that some piezo's have a circuit to drive them. If you have one of those, discard the driving circuit. Hope it helps. Regards

[dciocoiu]

I have that 130 in 1 kit too!

[Xellers]

Can you post a photograph of the completed project so that I can see the variable cap. too?