Making a Foxhole radio Very primitive
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- Опубліковано 2 жов 2021
- I made my own Foxhole Radio, the most primitive radio receiver. You can hear AM radio sound even without power.
Modified radio with soviet made germanium diode → • I got Soviet made germ...
Foxhole Radio wiki ↓
en.wikipedia.org/wiki/Foxhole...
Twitter: / ichiken_make
★ Equipment used (including amazon associate link)
Crystal earphone amzn.to/3ftxsue
Timber
Copper wire (enamel wire) 0.5mm, about 20m Obtained at home centers
Obtained at home centers, etc., about 20 cm of solid copper wire
pencil
Cutter blade
Wood screw
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music: Kevin MacLeod, The Big Beat 80's. - Наука та технологія
A tip - if you can find one of the old-fashioned blue razor blades, they work even better. The blueing on them is a microscopically thin film of oxide, and this works very well as a semiconductor. HTH
The bluing on the razor blade was selenium. Hence a selenium rectifier.
Nice pun! XD
I just bought a selenum based blueing paste.
So, I can haz kitchen-maid semiconductorz!?
@@freemanz4051 thats a good idea worth trying! never thought of birchwood blue! Brilliant!
If using a "true" razor blade, make sure its not teflon coated.
Radio Operators manual Q & A. Q. 3.74 Discuss the relative merits and limitations as used in power supplies of the following types of rectifiers:
(A) Mercury-vapor diode.
(B) High-vacuum diode.
(C) Copper oxide diode.
(D) Silicon diode.
(E) Selenium diode.
The only thing that you did not mention is that this only works with AM radio, not FM. I built many of these years ago in the 1950/60s. This was what got me into amateur radio, and electronic repairs years later.
Back in 1958, I had what was called a 'Cat's Whisker' AM radio - essentially the same thing. I would clip the 'antenna' to the bed frame to ground it.
He did show that it was an AM frequency near the end of the video. While the coil adjusts volume and the pencil changes the AM station you can deduce it is AM only given the information provided.
Also known as a crystal radio.
My uncle taught me how, in the 1970s, he built them (illegally) in wartime 1940s. I seem to remember a dead battery in the setup.
I think it replaced the razor somehow which we didn't use. It definitely was a dead battery, so there was no power involved.
@@d.marbus1493 The wikipedia article has a schematic that uses the carbon rod from a battery in place of the pencil graphite "Another detector design was a battery carbon resting across the edges of two vertical razor blades, based on the 1879 "microphone" detector of David Edward Hughes"
The most interesting thing to me, is that this works without an extra power source. The AM-signal itself is the power source.
Yes, that is the point of the video. You got it. Well done.
@@railgapHow snarky.
Definitely a fun project and is very important in times of emergency.
@@EmilyTienne😂😂😂
You tell em !!!
I built one of these many years ago as a kid. I used the cardboard tube from TP for my coil. Also if done properly the safety pin is let in it's original wedge shape with pencil lead attached with a dozen wraps of fine copper wire. Then just pushing down on safety pin it travels across the old school razor blade,and they is your tuner. I liked it so much that I bought a radio shack kit that used a germanium diode and a regular potentiometer for a tuner. With a wire about 100 feet long from my bedroom to the peak of the shed,I could pick up just about any AM radio station east of Mississippi from our home in Pennsylvania. And in the winter and night it was unreal how far stations would come in.
I ended up hearing foreign radio stations at night as they were bouncing off the ionosphere.
Oh that's so cool.
100 feet?!? WHo has room for a hundred foot antena on their property?? Did you live on a farm, then?
@@railgap not a farm but in very rural area. Room has never been a problem here. I'm assuming you live in a city somewhere. I've only ever passed through a few cities in my life. I can't imagine living in a city.
My dad bought me the Radio Shack version of this in the late 60’s and I remember using at an off grid cabin we had. At night I could tune in radio signals that were Spanish was spoken . We lived eastern Canada, so could those stations have been from Cuba or central America? Not really sure. I also could here some stations from the U.S. I still have it and when stumble upon it whilst rummaging through some of my things, I set it up and it still works fine.
I suppose the blade is a crude diode. Might as well just buy a diode. I made crystal radios as a kid that I stuffed into ball point pens. The pen still worked, but the clicker mechanism didn't (need that space for the diode). I wrapped the ink tube with fine wire I scavenged from transformers for the coil. It was not tunable - it just picked up whatever the most powerful AM station was, but it worked. I sold them to classmates who were amazed at the idea of a pen radio that didn't even need a battery. ...and yes, I became an engineer obviously.
There weren't too many diodes available in foxholes. But razor blades were readily available.
"I suppose the blade is a crude diode. Might as well just buy a diode." may as well buy an actual radio too. The point of this video was to make it the same way they did in WW2...
@@baseddoggie Unless you brought them along, you wouldn't have a crystal earpiece or wire in a foxhole either.
But they did :|@@eventhisidistaken
@@baseddoggie Right, because they *planned for this* or scrounged it from broken radios.
A couple of suggestions and a correction, the design actually dates back to WWI not WWII, this the correction though I am sure GI's in WWII still used them. Another point this type of radio will only receive an AM signal as you note and these are increasingly rare.
I think your use of the pencil end will work well , but if so it becomes the "crystal" as graphite the "lead" in a pencil is crystalline in structure. If so the cutter blade could be anything metallic to act as the contact. It acts as a rectifier separating the DC audio from the AC carrier.
In a more conventional trench/foxhole radio the crystal would have been a double or single edge razor blade. Preferable one where the manufactures name was carved rather than printed on blade and a double edged blade had still more surface. Any place the blade had been ground you'd expose a crystal. To made the needed junction you'd just need a fine piece of wire to serve as the cat's whisker. The trick is to find either with your setup the edge of the crystal. I think a classic cat's whisker works better but will try your approach.
One last thing, you didn't mention but I am sure you did. The point of the safety pin if you use your design needs to be in the graphite and not the wood of the pencil.
I'd also make two other points, in most modern American homes, plumbing is plastic at least in part as such water pipes no longer function as a ground, secondarily when using an electric outlet the best place to ground is to the screw holding the face place on.
Still it was a great video and there is much to like about your design!
A crystal radio will receive CW making clicking noises and if you can tune one to the FM band it will work if you tune slightly off the station.
@Marty Lampner - "the design actually dates back to WWI not WWII"
I rather doubt that, mate; the world's first commercial radio station was KDKA, based in Pittsburgh, PA, and they didn't go on air until *1920* - two years after the First World War ended. According to Jack Gould's book, 'All About Radio and Television' (1953), they were first reported as being used by Allied troops during the stalemate at the Anzio beach-head (Feb - May, 1944). The 'New York Times' ran an article on such radios on 29th April, 1944, describing one built by Private Eldon Phelps of Enid, Oklahoma.
Crean en Jesús Cristo y tendrán vida eterna y paz entreguénce a Jesús Cristo ahora mismo en oración Dios les bendiga
Les invito a una iglesia evangélica
What about P.O.W.'S Did they not utilize them too?
@@p.oneill6943 possibly… There are several great reads about WW2 POW camps. Many things were possible there, thanks to ingenuity and… lots of time. And also very importantly: befriending guards, trading with them (cigarettes and chocolate from Red Cross aid packages were good for that) and, if possible, getting damaging information out of them and then pressing them to deliver components. In Stalag Luft III camp prisoners even made a camera to make photos to use on false documents.
( several books on Colditz prison,
‘The great Escape’
‘The Wooden Horse’ etc.)
Built one as a child, only got one station, seems I lived too close to the transmitter. In the ground plane .... but it worked and the station was good , rock n roll. AM stations are becoming harder to tune in too many other signals . Fun project for kids none the less ....thanks for a trip down memory lane that kid is 70 years older now and had almost forgotten.
Neato! As a kid I had something like this, using a razor blade. That was about 75 years ago. Thanks for a super reminder of times gone past in the hills of Tennessee!
Wow, that is super cool!
That was about 75 years ago for me, too. In the hills of West Virginia.
My goodness how old are you two
How old are you guys? And how did you figure out how to make that
if you drop a variable capacitor in parallel with the coil you will have much greater control of tuning also the height of your antennae isn't nearly as important as the length the longer the better with frequency's this low and the best ground is still a couple of feet of copper rod driven into damp soil. Thanks for the video it brought back a lot of memories.
Yes.
Nice job, enjoyed the movie, but: Along this same theme, the purpose of the wire wound induuctor you formed is to be part of an L/C network to select a single station from many. The inductance of your wire-wound coil becomes resonant with the capacitince of the long wire antenna. Since your implementation lacks the long wire antenna (which is too short for the AM band, and thus capacitive) the inductor never resonates, and you don't get a "tuning peak" while trying to select a station. As another commentor suggested, you might want to add a parallel approximately 100-300 picofarad capacitor connected between your coil standing end and the sliding tap contact. That way you can continue to use the handy pickup loop coil inside and use resonant station selection by sliding the coil tap.
Bad tuning and to some extent volume is mostly because coil is too low Q (it looses energy because of resistance, capacitive leakage, proximity effect, skin and other things).
make the coil on a thin plastic bottle about 70-150mm diameter you want as little material close to the coil as possible especially inside it (highest magnetic field concentration) and as good insultor as possible, so polystyrene, polypropylene, PEHD plastic are best but PET or other plastic tube works better than the wood.
make a space between turns (ideally 0.6 times wire diameter) just winding same diameter fishing line between the copper turns to keep them separated has worked many times.
I could go on about designing crystal radios for a loooong time. literally days.
basically the better EVERY SINGLE component Q is the more energy you can get out of the system, and you can NEVER get higher Q than the lowest components Q, so you want to make every effort to reduce losses.
the antenna and ground will always be the biggest loss, but if you have a second coll loosely coupled inductively (two coils near each other will make sort of a transformer) to the one connected to the antenna and ground you get bit more out of the system.
add a variable capacity parallel to the antenna coil and you can create resonance in the antenna further increasing the available power, add a second variable capacitor between the ground and antenna coil and capacitor for even better tuning.
now the detection needs just a coil with a parallel variable capacitor a diode and phones.
to get more out of the phones you may want to make an impedance matching unit, that is a HUGE subject all its own.
a coil made like in this video has a Q around 200. a similar coil on round Polypropylene plastic pipe would be roughly Q 350 to 400, so about twice the energy in the system...
now use 1.5mm copper spaced so one turn is 2mm on a 150mm round Polypropylene plastic and we go to Q 600. each step gives higher voltage and better tuning (theoretically Q100 to Q 500 is 5 times the voltage and as resistance is same available power is 5x ...)
When I was a kid in cub scouts (back in the 50's) we made project crystal diode radios. Amazing that they worked so well. Thank you for sharing this video.
When I was young, my father was still using the radio he built in early 20’s, based on this principle.
Built my first crystal set in 1965 at the age of 5 all by myself. Tesla invented this thing to be honest. He just didn't have a tuner and called it his Ghost Radio because it sounded like thousands of voices at once - which is exactly what a wide spectrum receiver sounds like.
Thank you for posting, Very interesting more basic than a crystal set.
Thanks for taking the time to translate and dub this. 😊 We appreciate the kind gesture
lived close to a main am station some 50 y ago. an old-school telephone ear piece connected by a diode to a metal mass like a tap was all you needed. used to listen to that "radio" in the bathtub. btw, a greenspan corroded cent works as a semiconductor, as well!.
My dad was into electronics (all tubes) had his little bench with oscilloscope, signal generator, signal tracers, and so on. When I was little he put together a crystal set for me and place a headphone on my ears. Wow didn't expect that, it was magic for a little boy, put an unforgettable smile on the face. The AM station came in was so clean like true HiFi, better than any radio at the time and even with today's components, pretty loud as well connected to a raw speaker. Free energy!
More like free information (or entertainment) rather than free energy
@@syedabishosainrizvi7817
joule = volt × coulomb which is the driving energy in moving the speaker cone translating into sound. In other words free energy for the end user, although it takes a fair amount of energy to transmit the signal at the broadcast station, but you get it free with a crystal set.
The oxide layer and a point contact works, but a better one is a lead-sulphide crystal that is easily made by mixing lead filings with sulfur, and melting together in a test tube, and cooling slowly. The crystal made, is usually surrounded with leftover lead, making that one contact, then a wire 'whisker' is used to find the 'sweet' spot, where reception is greatest. I made one some 60 years ago.
the down sides of lead tho granted up untill the year of his passing my dad did use lead in his bullet castings so .......
@@ferrofeles2063 I'm a reloader/caster as well. Honor to the memory of your dad.
Lead is fairly safe in truth. If casting, you need good ventilation. Outside with a fan is best.
Its the fumes that are dangerous. The lead itself? Wash your hands when finished and dont snack while leading lol.
This interests me! I thought at first you were speaking of pyrite.... these ingredients are on hand for me! Thanks for this!
Where is the power fixed?
@@zakayokiplimo-mv3pg in the radio signal itself!
My dad use to make those radios all the time when we were kids, but he used a turner on his radio that had a knob, and he used a long wire Antenna. They work all the time.
As several others have said, a rotary air-dielectric capacitor of several hundred picoFarads would give you the ability to tune it, rather than have all the local AM stations coming in. These capacitors are used for tuning AM radios to different frequencies and you'd probably get one from an old AM radio or a radio amateur's shop. My first radio was a crystal set using a galena crystal (lead sulphide) with a fine wire point your could move around to find a good spot. Ordinary headphones worked alright.
You can also make a variable-inductor version, two paper tubes, one sliding inside the other, and a wire coil around each. As you move the coils, the inductance changes, and thus the tuning.
I never tried one in a radio, but I saw an experiment done where a variable capacitor (about 100 pF value) was made using microscope glass slides (the thin ones that are "cover slides") and aluminum or copper foil, in layers. Copper foil is readily available since its used by guitar home-builders, and it can be soldered to. In theory, in theory, ordinary plastic food wrap could be used as the dialectric layer in a home-made fixed-value capacitor. Won't work well for a variable capacitor.
To get really fancy, it's possible to make simple vacuum tubes using small tungsten filament light bulbs (old-style car turn-signal lamp bulbs for example) with a bit of metal, or fine wire mesh around the bulb. Somebody has posted a video "how-to" about that on UA-cam.
DC voltages were provided by using 9V batteries in series. It's possible to get several hundred volts DC at low current, and the battery "snap" connections make it easy to connect them in series. It's necessary to be very careful about exposed connections. Even at low current, several hundred volts gives a very nasty shock. If you try this method at your own risk, the "One hand in your pocket" rule applies!
It's much cheaper to buy a box of 24 or 48 of 9V DC batteries from an industrial supplier, compared to retail prices for one or two 9V batteries.
@@flyingbeaver57 It's great to hear all this from your experiences. Like you, I've seen a UA-cam video recently on how to make your own vacuum tubes but it wasn't so simple, as you had to make your own glass-to-metal seals. I've done a lot of experimenting over the years too, and somehow it's very satisfying to find how to make do with minimal resources. The first time I ever used a vacuum tube was with a battery for the filament and a 90 volt battery for the plate, with earphones in the plate circuit. You could hear the "sound" when you drew a finger across the grid terminal. Amplification, olé!
Wonderful video. I liked the fact that you let us see both the things that worked and the shortcomings of this radio. Thanks for sharing!
Technically, the carbon in the pencil is a semiconductor. That is part of why it works as a detector.This sort of radio is also called a "foxhole" radio. Small pits that people dug during the war got called "foxholes"
This design will never be selective enough to select between stations that are near each other on the dial. A loosely coupled radio does better in this. In those, the antenna connects to a second coil that is placed near the coil in your existing design. Ideally both coils are tuned and the coupling is adjusted by moving the coils together and apart to find the best distance.
Nobody on any of these UA-cam videos actually knows what they're talking about.
1) They didn't "invent" these radios in WWI for "entertainment. They were used to disseminate information to troops without using normal radios that could be detected by the enemy because of the oscillations in the regenerative circuits that emit RF.
2) Many things can be used to make a detector because these are NOT normal diodes and the "crystal" has nothing to do with anything. These are TUNNEL DIODES and always have been- but has never been recognized.. What matters is that there be TWO DISSIMILAR conductors (for different "work functions- look it up) and the KEY is a very thin insulator like a layer of oxide like the bluing on a razor blade,,,but many oxidized metals like corroded pennies or galvanized tin will work with the carbon pencil lead.
These are called CIC Tunnel Diodes; they are NOT the normal semiconductor tunnel diodes. No semiconductors are involved here. CIC stands for "Conductor/Insulator/Conductor. The early Heaviside detector used a needle lowered through Olive oil to a pool of mercury; the olive oil film on the steel needle is the insulator. The trick is to get the insulating layer thin enough for electron tunneling to take place. Again- THERE IS NO SEMICONDUCTOR INVOLVED. Tunneling occurs in BOTH directions, but because of the different WORK FUNCTIONS OF THE CONDUCTORS, there is a net flow on one direction and THAT is why it can be used as a detector!
@@craigwall9536 - "Nobody on any of these UA-cam videos actually knows what they're talking about."
Most of, THAT INCLUDES YOU, Mr Clever Clogs. Show me one piece of *EVIDENCE* to back up your claim that they were NOT built by troops for their own entertainment, but were military issue!
FFS!! By the time foxhole radios were invented (early 1944), military electronics was up to building radar sets small enough to fit into RAF Mosquitos and similar-sized aircraft - so why on earth do you think that they'd rely on something as crude as this to disseminate vital military information to troops?
You may know a hell of a lot about semi-conductors, but when it comes to commonsense and rational thinking, you'd be left behind by a reasonably intelligent *fencepost!*
Thank you for that detailed explanation
@@craigwall9536 I suspect it's merely a translation issue, no need for all caps Sun will rise tomorrow. People refer to diodes as semiconductors often and it will not stop. SCR's, Thyristors, etc, the tech grows faster than vocabulary and Diodes are merely P-N junctions of the same substance many transistors are made of Germanium, etc. All translations deserve some wiggle-room.
@@craigwall9536 Radio receivers in WW1 could not be detected by the enemy for their IF emissions! It was the antenna that might have been observed. Far more interesting were the transmitter locations. Any non-ohmic conductor or junction is a semi-conductor, that includes, wood, clay, ionic liquids, gases, semi-metals (As, Ge, Sb) and insulators. Only some metals are "true" i.e. ohmic conductors, in that they follow Ohm's Law.
Wonderful! And I learned: you can make a diode with a cutter blade and a pencil. Thanks.
Knowing how to make a diode from a razor blade is really cool.. the 1st time I saw it i was amazed.. 😊👍🇮🇪
Thats great, no "power" needed...
I had done those more than 40 years ago.
Please more.
Thank you! I have been waiting so many decades to find crystal earphone! These devices were brilliant!
I made it with blue razor blades and hardest pencil vey sharp, it works as the "cat wisker" germanium diode 1n60, also worked at hi volume on a high impedance magnetic earphones at times when AM stations had over 10 kw power, got stations over 50 km away, tuning with a variable capacitor, also needs good ground and long antena
We made similar, called a "crystal set" . Then AM radio became FM and that was that really. Lots of fun in the day. ❤
The exact design he presented was actually used by the US soldiers during WW2 in Europe. They used a blued razor and a pencil tip. It was called the "Foxhole Radio"
I've built a few of these over the years. Excellent instructions sir.
Interesting bit of history and a cool little project. Thanks.
As a kid I had an electronics kit that had instructions for a trench radio, and it blew my mind. It was like magic hearing a radio station without any power being used, simply using the power of the transmission itself. I could only pick up one station, and the ear piece was garbage and sounded really rattly and distorted, but it still amazed me regardless.
あなたのビデオをとても楽しんだ。ありがとうございました。
Daijobu! Amazing, it looks like the graphite acts as a “diode” of sorts 😅🌟
I had a crystal radio when I was a kid in the late 60's early 70's. It had about 70 ft of copper wire out to s tree in the back yard.
It had a potentiometer for tuning and a diode. We were fairly remote, but I could get the local am station. Also as mentioned by others I could hear stations far away at night.
On a slightly different note. In the late 70's I had an old radiogram that could pick up Egypt from Australia at night.
Thank you Very much for the video , greetings from la Calera Chile Southamerica
The wire looks like it is enamal covered. The slider tuner needs to be in contact with every wire as you slide it along. You must sandpaper off the enamal wire where the slider contact the coil. Also, the coil is only half the resonant tuner. A capacitor in parallel with the coil is required to tune the range of frequencies. f=1/(2*pi*square root (LxC)) where f is the frequency, L is the coil indutance, and C is the capacitance of the parallel capacitor. Also, the crystal should be tapped on the coil to retain selectivity.
Thank you! Very Cool! I was just looking for information about building one of these. This video was a big help. Much appreciated!
Thank you for your efforts and the nice demonstration. UK
LOOKS REAL GOOD DUDE! FOR THOSE WHO DON'T KNOW THE EARPHONE MUST HAVE VERY HIGH IMPEADANCE SO IT DOES NOT LOAD DOWN THE VERY LOW SIGNAL DETECTED . YOU COULD USE A IMPEADANCE MATCHING AUDIO TRANSFORMER THAT HAS HIGH IMPEADANCE ONE ONE WINDING AND LOW IMPEDANCE ON THE OTHER WINDING. .
I remember making one of these for a science fair project back in 1978.
The trench radio got its name because it was used in wartime. It was so simple to make that even POWs made them. What I've never heard is where they got the headphone from.
I have heard they used tooth cavity to catch Morse code.🤯
Nice work and explanation!
Soldiers use to use double sided Safety razor blades Blued with a coating that acted as a diode like detector.
Bad earpiece and speakers. For proper functioning, the resistance of the earphone or speaker must be about 2000 ohms. In addition, AM stations are very few and far between, and if they exist, they do not have the required kW power. In the 1960s it would have worked satisfactorily, as the power of AM stations was large - more than 10kW). Today it is only tens of W. It would be best to apply a Galena (PbS) crystal and a very thin tip. A strong pencil lead is very inappropriate. The tuning coil is not tuning, but has a very high resistance for a specific signal, so the signal of a specific frequency goes directly (short-circuited) to the detector, which removes the positive or negative half-wave and thus induces a "pulsating" potential in the earpiece. The "tuning" coil is therefore useless, because you certainly don't have several AM stations within range.
Thank you for making this
Haven't made one of these since I was a kid in the 70's. Something for me to try out again! Thanks for the video!
I could hear Cuba at night from Naples Florida on mine. K4IVK built one from roadside trash. He was awesome! Rest in peace, Victor.
Awesome! Thank you for this tutorial!
Thank you for great instruction❤
Technically the cutter blade and pencil together make a diode. Not a very good one but a diode none the less. The other way of doing it is a blued razor blade and a safety pin with the point resting on the blueing. Again that makes a sort of iffy diode. There are also some types of rock you can use as discovered by Jagadish Chandra Bose
During ww2 wen I was in A Starlage luft prison camp I made loads of these radios for the prisoners and they wer great..my old mum was awarded the iron cross first class with golden oak leaves and diamonds in solid 42 carat gold by Hitler for her work as a Grenadier SS tank commander on the Eastern front..
Excellent! Thank You for sharing.
When you sanded the wire it would have been too easy to get a shorted turn.
It's better to make little loops by twisting the wires around and use them as taps.
It's also better to use a hollow cardboard tube as water in the wood takes away the signal.
The sharp edge of the razor blade against the pencil would make a better diode.
I know they're not too common in US, but I find the copper radiator pipes to be a great source of ground / antenna
Awesome information. Thank you Brother !!
Very fascinating to see a crystal radio diode been created without, germanium. I have seen example of a diode made of copper and iron.
Extremely important and useful information
Thank you for this. Awesome.
Great job. Thanks.
About sixty years ago, I built a kit very much like this, my first radio build. I spent some forty years in electronics, been mostly ignoring it since it went digital and woke. I believe I had a lead, galena crystal for my first few. Lots of interesting comments.
What do you mean digital and woke?
@@Komiksti He is probably referring to the fact that modern tech companies that manufacture digital electronics have dove headfirst into DEI and affirmative action nonsense.
Thank you very much!
👍very simple thank you for the inspiration
While the design dates back to before WW1, I would imagine it would be used more in WWII. In the first world war there was no radio for entertainment or news like we know of today. The only thing to listen to would be messages in morse code. Even then you would have to know how to decode the messages. There was very little actual speech transmitted. By the second world war the crystal radio was widely known, and could easily be built by a soldier in the field. There would have also been radio stations to listen to.
A frequency filter would help this. Its pretty much the same thing minus the ear plug. You have it in line with the antenna. You set up the receiver to hear the powerful local station and use the filter to tune it out. can be VERY handy!
very primitive - so crystal - wow - many winding.
Thank you!!❤!
West: "Muh pronouns"
East: "Here's how to build a radio."
Well cleaned Zinc plated steel washer, carefully heat washer to dull red heat.
Bluish vapors means it's about right.
Allow to cool.
Use just line a 'blue razor blade' detector.
Zinc oxide/zinc metal interface has semi-conductor properties.
Correctly biased, zinc diodes have a narrow 'negative resistance' region, allowing amplifiers and oscillators to be made.
Not much gain and it has lots of parasitic capacitance, so it can't handle higher frequencies very well.
Man that is super cool!
thanks for sharing
Cool man ! I can dig it !!
Coil+Capacitor creates a tuned circuit. You can easily make a compression-type variable capacitor.
Every kids should know how to make a radio, this was awesome!!!
Really cool I love to see people build incredible things out of scrap
Nice video thanks
Very interesting project my friend ❤ I will try this myself ❤
Ok , well cristal radios don’t have much volume to begin with . But I took notice that when you cleaned the enamel of the coil , you forgot to clean the cats whisker , so you still fighting with enamel . The enamel acts as an insulator . But good demonstration anyway .
Um cristal ear phones . I didn’t know someone was still making them .
Can you tell me where you got yours ? Thank you 🙏.
the pencil graphtetti and clay mixture and blueing are semi conductors and the npn pnp samwitch(transistor)
there accutly a great way to learn what those are and how there made like chemistry of it
odd fact solar panels where discovered by
"opp case poped off the sun light broke the computure by adding current at the npn pnp transistors"(1950's how long solar panels have been around)
My dad made these as a kid in the 1920's.
He became a radip operator for SOE in WW11...
this is freaking awsome !
This only works if you have an AM station VERY near. Or buy an OA90 diode and use this instead of the pencil.
I made me one of those in 6th grade. I used old EM radio headphones. I used a single edge razor blade and the lead out of a pencil for the detector. My coil was 120 turns around a 2 inch paper roll. The coil was not sanded but connected to the antenna on the end. . IT WORKED! NOW try a TRANSMITTER with an induction coil (From an auto) And a relay coil wired to vibrate to deliver a pulsed current (from a battery) to the coil . Wires from the coil can work a SPARK GAP. One pole of the spark gap goes to ground and the other to an antenna wire. A code key can be used to make and break the connection to the relay.
Better go answer that knock on the door now. It might be the FCC.
Its something good to know if you get stranded on a desert island--- You could use the engine parts to make a radio to transmit an SOS.@@randykelso4079
That's so cool!
Being AM you may want to rotate the whole assembly; works best sideways to the transmitter.
I agree with J Campbell....the length or the antenna is the key. @ 900khz a full wave antenna would be 333.1 meters or 1092.8 feet. So a 1/8 wave antenna would be 136' for 1/8 wave at 900 khz. And not coiled up as shown,but stretched out it's full length.
I used to stay up late on Saturday nights using the crystal radio my dad made, to listen to Jean Shepherd broadcasting live from New York. Jean Shepherd wrote the book "In God We Trust, All Others Pay Cash" from which the movie "A Christmas Story" was adapted.
The radio does use a semiconductor. The oxidised cutter blade and pencil lead form a primitive schottky diode.
Actually, it forms a TUNNEL diode. But NOT the PN type. This is an MIM or metal/insulator/metal diode. The two metals must have different "work functions" so that one gives up electrond more easily than the other. Which is why carbon is usually substituted for one of the metals.
You explained better and properly
This in fact does use a semiconductors as pencil graphic has semiconductor abilities
I think you should tell people that you're using magnet wire and that what you say is smoothing the surface of the wire and removing loose ends is in fact sanding the enamel insulation that coats the wire away down to the bare copper wire for all the obvious reasons. Maybe you didn't know.
Also the fact that you get your electricity from thin air (literally) is amazing
My father taught me to make one with a box spring mattress as the radiator when I was just a squirt.
Thank you very much for your video. It was comprehensive and visually interesting. It was paced nicely. In particular, I enjoyed your trial and errors you expressed in the end.
During World War Two, where would a crystal earphone come from?
How about high impedance earphones?
As a kid, I used a 600 ohm microphone that acted as a small speaker under my pillow, and used the bed frame as my antenna and the outlet plate screw as a ground!
❤ cool thanks for sharing
Instead of the blade, crystal diode will do the job.And for sound output old rotary telephone ear piece (with a metal diaphragm)is the best.
Bravo !
Blued razor blades work better, especially is you wet them and put a few grains of salt on them so they create rust spots, then touch the rust spots for an improved detector. I think your coil is a bit large. You could also make a paper compression capacitor in parallel with the coil to improve the tuning.
...well the tempering by flame is blueing .
You forgot to give the width of the board used.
There were plans published for a crystal radio that had it's coil wound around an Quaker Oats container. People a generation later trying to make these radios could not get them to work. Quaker Oats had changed the size of their Oats containers to a smaller size and it changed the frequency range if wound according to the old plans.
Clear plastic bottles are probably the best choice today. Plastic has much lower loss than either cardboard or wood. Wood is a very bad coil form choice, being variably lossy, depending on wood type and water content.
Same applies to the base, plastic would be better.
As a boy scout we all made one of these , but used a Gillett razor blade not a utility knife . All twelve of us passed lol . Mmmm might of been cubs we were around eight or nine years old
Nice demo. One comment about grounding to the faucet....a lot of plumbing here in the states is plastic, not copper or other metals.
amazing
This kind of reminds me of Prison Hacks. Very neat!
the pencil graphtetti and clay mixture and blueing are semi conductors and the npn pnp samwitch(transistor)