When I was about 12 years old in 1965, I found a book in the library on how to build a Foxhole radio. It was similarly built like this one. The oxide on the razor blade and the carbon from the pencil lead made a crude semiconductor diode. It required headphones with 20000 ohm impedance, which I lucky enough to find. My father was impressed when I had him listen to it.That project made me want to be an Electrical Eng. Because of it, I ended up with a Masters of Science Deg in Electrical Engineering from CMU.
I got three such Magnetic 2000 Ohm headphones - - one from the 1930's, but one side of it doesn't work anymore :-( I think it may be internally shorted
@@Jeffrey314159 I got lucky. I got mine from the garbage pile of a retired ham radio operator; It didn't have jacks to plug it in, but both sides worked.
Read the same book. Did the same thing and later converted to a crystal diode. I was 12 in 1965 as well and made several things including model rockets. I’ like to go back for a day and see that time in life through my eyes as an adult. It was just magical with all that was going on at the time. Thanks for sharing.
As a teacher, I encourage everyone to pass this on to any child you know. This is the kind of stuff I wish to see kids playing with-like when we were kids ourselves. I think a lot of us come from times or even situations where we didn’t have much. I’m relatively young at 44, but in the 80’s as a kid playing with antenna shapes, lengths, materials and positions was more because we didn’t have cable TV. But it was fun and rewarding. Foxhole radios were an accessible project cause you could ride your bike around to find the materials. A little adventure and discovery would be beneficial to todays kids.
This brings back memories when I was a young boy of ten my dad and I made radio and tuned in the cat's whisker to hear a radio station the wire aerial was looped of the clothes dryer in the kitchen now I am 73 and this brings back the memories of my dad helping me, loved it thanks
I like this. No nonsense, no bullshit, no clickbaiting, no stupid intro. Just a genuine how-to video while showing you all the necessary steps and highlighting with captions the important bits. Very neat. I applaud this RU-vidr for being so down to Earth and helpful and providing quality entertainment. A+++
I can't understand why handmade diode working. In case of commercial ones, there are two different alloyed silicon plates, to provide conductivity only through one side. How does that work kind of scares me. sry for bad English))
I was making these when I was around 10 in the 50s. I used a capacitor in parallel with the coil intended to be resonant in the am broadcast band. I used Galena for the detector. Next came regenerative tube receivers, tech school, ham radio and commercial FCC licenses and a nice career designing and building custom laboratory equipment for a major University medical school. Now retired I still operate ham radio and sometimes scratch build things for the fun of it. I also still have some pieces of Galena just in case ...
joe woodchuck ... You`ll absolutely love this website about radio history. There are so many free PDF books and old magazine issues that it will boggle your mind! Check it out! www.americanradiohistory.com/BOOKSHELF-ARH/Bookshelf_History.htm
@@tomjones239 Looks like a wonderful resource. I wonder who else remembers Whites Radio Log. It was a listing of listenable stations domestic and overseas. I was mostly interested in the shortwave listings, but the domestic stations were also fun.
@@joewoodchuck3824 nice, I like reading these stories. Im 28 now and I had 0 knowledge about electricity as a kid. I just had some fun with magnets, that all. I wanna build some radio soon. Electronics seems awesome.
I am here because of the tv show All The Light We Cannot See. In my teenage years (20 years ago) I liked listen to the radio, but knowing now I didn't liked it enough. Building this kind of radio is cool. And I didn't knew it was possible with materials like this.
Hey, Lilly! Thanks for the questions. I've watched your videos before and really enjoyed them. I don't know the polarity of the two speaker wires and I can't find an exact answer anywhere online. I keep flipping back and forth as to what the right answer is based on how the radio works and what I know about speaker polarity conventions. If anyone knows the answer to this question, please let us know. With regards to your diode question, only some schottky diodes will work. If you are going to use a commercial diode, I recommend a germanium diode (like the 1N34A diode) because they have a lower forward voltage drop which make them work well for a radio like this.
Over Engineered Ok thanks for your answer :) I ordered some germanium diodes now. I think that maybe the speaker wire that comes from the ground has negative polarity. I might do a video on crystal radios, If I do I will link your video in my description :) Hey do you think that maybe I can connect a battery to the coil instead of using an antenna and ground connection?
+ Survival Lilly Thank you for the reference in your future video! When you asked about the polarity the other day, I looked into what it really means for a speaker wire to be positive or negative. It is confusing because typical speaker signals are alternating currents (variable currents also works, just not as well). Because of this, speaker polarity is really just a convention and mainly matters if you have multiple speakers so you wire them up consistently. If you aren’t consistent between two speakers, they will be vibrating in opposite direction (as one is moving outwards, the other is moving inwards) which could cause some destructive interference or damage to the speakers if they are in the same box. You can test the polarity of a speaker by connecting it to a battery which will make the speaker cone move in or out (depending on the direction that the wires are connected to the battery). When you connected the battery to the speaker wires in the direction that moves the speaker outward, the wire which is touching the positive terminal is the positive speaker wire according to convention. Given all of this, I thought about how my radio works. en.wikipedia.org/wiki/Crystal_radio#/media/File:Amplitude_modulation_detection.png This image from Wikipedia explains how the diode rectifies the radio signal and how the changing amplitudes are what create the variable voltage/current which creates the vibrations in a speaker. This is a little different than typical speaker signals because it is not a full-out alternating current, it is just a variable voltage/current. As a test, I used a multimeter to check the DC voltage/current of the signal from my radio and found that the reading is always positive when I connected the positive lead to wire #1 (and negative when the multimeter leads are reversed). This leads me to believe (just like you are thinking) that that wire #1 is the positive speaker wire according to convention. Because, if you connect the positive side of a speaker to wire #1, the speaker cone should move outward as the the voltage/current in wire #1 becomes more positive. However, I’m not an expert on this and could be wrong. The good news is that it doesn’t really matter what side is technically positive or negative :) but it is interesting to think about. Also, I tested your idea of using a battery instead of an antenna and ground and didn’t have any luck. Let me know if you have any issues with your radio. Keep in mind it only picks up AM radio stations. Hopefully, you have some strong AM channels near you. My radio is about as basic as you can make. Using a germanium diode will improve it for sure. If you really want a better radio, you may want to use a piezoelectric earphone or add a variable capacitor like the one from this website: rimstar.org/equip/crystal_radios.htm. Have fun!
When I was in college I was in jazz band. One day we had to use a very very long wire for a speaker cable and it was coiled in the corner. it ended up picking up radio signals
With a strong enough AM signal, many things will pick up the signal. My friend's house used to have a local radio AM transmitter about 200 feet out from his back yard, before local radio shut down AM. At night, you could hear the radio signal being picked up by things like powered PC speakers (powered up, but not plugged into anything) and the amplified speaker on a tape answering machine (when those were a thing)
Thanks, Many memories! I made the identical radio in 1955 when I was 10 years old. A book in our school library "How to build a foxhole radio" was the motivation. I've looked for a copy for years it had such a big effect on my life. I had no help and everybody thought I was nuts. I ordered a pair of headphones from Allied Radio in Chicago which were sensitive enough to make it work. After I showed it too my Dad I don't think he ever questioned my opinion about anything again. He was very impressed and told everybody about it. Life was simpler back then.
Hi, i saw your comment, and i have to say there's another person down this video, that had almost the same experience as yours and that built a foxhole radio in the 50s, so maybe you've something in common. The person down this comment section is called Roy Jackson and another one called joe woodchuck
This is amazing. This is how people of great knowledge back in the days make discoveries like the light bulb and generating electricity and cars. This is how products start originally before it hits the production line. You are a man of inventions. 👍
Fantastic! The parallel L-C circuit with a variable inductor followed by an envelope detector for the shortwave AM receiver.The way you made the diode for the envelope detector was pure genius! 👍👍👍👍🙏
we built crystal radio set's for boy scouts when I was a lad.. this was fun to watch and will be a great project for my grandchildren and I to do this summer..!
Incredible diode engineering there! I use to love making crystal sets in my dad's shed. I remember a few experiments I found in old books. One was sheets of aluminium foil between pages of a book to make a variable cap. "Ground" for me was actually ground! Used to hammer a piece of copper pipe into the ground and use that.
Like many others here, I also made crystals radios when I was a boy in the early 1950s. First one was a kit that my father bought for me, but then I started to build for my friends. First versions used a galena crystal and a cat-whisker for the detector. But then I discovered solid state electronics in the form of an IN34 germanium diode that was more reliable than the crystal and cat-whisker combo. Went on to build many other electronics projects over the years including two early personal computers when they first came out in the mid 70s.
@@huseyinuguralacatli5064 Yep, you can't really drive a full sized speaker without additional amplification but you can drive a really simple earbud style headphone using just the energy from the radio waves.
Next try a primative tank circuit AM transmitter transmitting on 1.6 megacycles. The range will be limited but the circuit is extremely simple. If you dare, you can amplify the signal later and make a clandestine AM radio station. I made one as a child that transmitted just under 8 kilometers. But a simple one transistor circuit is really simple and will transmit about 100 feet.
Better radios exist, obviously, but none capture the 'magic' of trapping voices and sounds out of the air as well as this one. Really makes you feel what a mysterious beauty it is to be surrounded all the time by these million voices from nowhere and everywhere, ready for you to catch them.
They actually say ghosts are something similar and just because you can’t see them doesn’t mean they are not there just outside the visible light spectrum
Im in my 70z now and as a kid we all made what was called the Crystal Radios. Fun for a time when the toys everyone now has was called science fiction, Piezoelectric, A world of energys were still discovering. Nice vid and thanks for the memories.
You just taught me a lot! Thanks for sharing your knowledge! I'm gonna go try it at home. Pray that I don't catch my garage on fire, I'm new to this stuff. 😁
When I was in the third grade back in 1959, we build this style radio for a class project. We used the transistor radio earpiece as a speaker. So cool.
I made one of these when I was in 6th grade. It was a science project. It worked great. Used to listen to baseball games on it. Never need any batteries.
Great video Way back when, when I was an industrial arts teacher, I had my 7th graders make crystal radios. I had the roof of the school loaded with long runs of copper wire. The kids were amazed that they worked with no batteries and from such simple materials. So sad those programs were dismantled as being part of an industrial past, and how even the term technology has been hijacked. I also had a toilet in the shop, and one which had been sliced in half so they could see how it worked.
Ça a l'air d'être relativement facile à fabriquer mais rendez vous compte qu'il y a plus d'un siècle, fin du 19ème, les prémices de la radio étaient déjà là. Quel génie inventif il a fallu pour arriver à ce résultat ! Il en a fallu pour ça des étapes de recherches. Et c' est finalement Guglielmo Marconi qui lance la première expérience de TSF. Quelle invention magique tout de même ! La TSF, télécommunication sans fil, c'est une fenêtre ouverte sur le monde, longtemps avant internet.
More fancier than my old Boy Scout days in the 60's. We used crystals instead of diodes. GREAT VIDEO. Really enjoyed. Brought back good memories. THANKS.
Hi everyone I built a radio similar to this from my dads boy scout manual from a long time ago. To date my self it was back in the fifty's and I was only 6 or 8 years old and he helped me put it together. I was so surprised and overwhelmed to hear voices and music from this copper wire and a crystal and a small speaker. IT WAS WAY COOL and I will never forget it. I'm so glad to find this video I'm going to build another
I made a crystal radio kind of like this using an earphone in junior high school 1963. I would listen to the AM radio stations at night. Then we made a magnetizer for magnetizing a screwdriver. The most fun was the shocker. Two small metal pipes attached to a cardboard tp roll wrapped in copper wire with a contact point to energize the pipes. They only let us wrap it once but some kids wrapped it multiple times for a jolting experience. We used to see who could hold on for the longest. I think that's when I lost most of my memory in junior high.
One of the first things I built. I used a variable capacitor and a fixed coil. Clipped the aerial to the metal frame of the window and earth lead to the water pipe. I used a crystal earpiece to listen to the radio. I was hooked. Spent 45 years in the electronics industry, now I’m retired.
That's amazing! I thought that diodes would be much more advanced than that. I'm aware the quality will probably not be the same quality as diodes you can buy but still
The heated part of the razor developes a coatinng thats super thin. Thats the insulator in the diode, then the graphite acts at the pos and the metal acts as the neg. At least that what i can assume
very much like a crystal set i put together on Christmas day 1967; you got 1, count’em 1 crystal, had to wind the coil and run the antenna. it was the deluxe $5.00 model (blue) and came with an single sided headphone. we ran the antenna on the roof - got most am stations in the sf bay area! i was 14. if in tact, it would still work today...
Yep, this was in my Boy Scout Manual in the '60's... my dad was a ham radio operator and had our cub scout den make little radios with diodes and tuners and a AA battery all in a clear plastic case. An on/off switch operated by a tube containing two wires and a drop of mercury, stand the case upright, the mercury joined the power wires, lay it down, the mercury slid away breaking contact! Of all the stuff from childhood that is what I still had!!
Made these in the 1950's. We used to Shellac the TP Tube for strength and after winding the wire to keep the wire fixed. Enjoyed the Blueing of the Xacto Knife blade. Back in the 1950's they sold Blue Razor Blades; that's what we used. You can replace the Knife / Razor Blade with a Germanium Diode, they are still available. The Polarity for the Speaker connection isn't too important; technically it's AC. You could try swapping the leads to see which one is louder. We didn't have Stereo when I was making these, we used Headphones. Could try Ear Buds maybe. Good Job!
I made one like this when I was a kid..50 years ago. the trick is the crystal diode and the head phones. It worked with power sorce and it cost almost nothing
My uncle was a electrical engineer back in the 40s 50s 60s 70s but in the 50s he had his own radio show in the Chicago area he would teach you how to build a radio on the radio. He also moonlighted as the masked terror the local wrestler.
I had a Remco Crystal Radio Kit about 55 yrs ago that wasn't much different. I remember winding the copper wire, and sanding the insulation off. It had an actual Diode in it. I grounded it using the heat duct, and used the aluminium window frame as the antenna.
Sure brings back fond memories. I used an 1N34 germanium diode for the detector. I ordered it from TV Craftsman in my home town. It took 2 months before I could pick it up. When Radio Shack was still in business, I buy a packet of 20 for $5.
0:15 This was from a CRT, right? 2:00 I recommend you to solder this, its a better contact. 4:35 Excactly THIS reminds me back in my childhood (mid 90´s), as a built a crystal radio. Today, around 25 years later i still get goosebumps at this moment when the voice comes out of the noise. Greetings from germany
It's kind of cheating to hook it up to an amp, because the amp will contain transistors and high impedance. To see if the home-made rc/diode circuit is really working, you need to use something akin to a crystal earpiece (piezo device).
I made one of these from a kit when I was 11. It worked but would only pick up the one AM station in town. But no batteries I thought it was a miracle - still do!!!. 👍👍👍
Replace the pencil lead/blade with a 1N34 and you would have exactly the same radio I used back in the 1950's. My first radio. But I didn't hook it up to an amp, I used a crystal earplug phone. It worked amazingly well for such a simple rig.
A crystal radio. I built one in sixth grade shop class. It looked nearly identical to this one, except that we didn't create homemade diodes from pencil lead (graphite), which is really fascinating. My radio could never receive more than one or two stations, and that was only on certain days, presumably when ionospheric conditions we're optimal to reflect AM signals. When this occurred, I would often hear broadcasts in French, probably because I was receiving Canadian stations. (I was in the Boston area.)
Built one as a kid in the '50s. I'm still building radios based on the ingenious early designs of pioneer hobbyists. I restore historic commercial radios too.
I have been building xtal sets for decades. Lately I've been using spiderweb or "pancake" coils. I mostly use homemade or vintage parts. I have a spiderweb coil from the twenties with cotton covered wire that was shellaced. Recently, I heard a station 300 miles away with a headphone that's over a hundred years old.
My father grew up in the 20's and 30's. He said he made extra money by building crystal radios from the coils he recovered from the starter motors of Ford cars.
Cant stress this enough, De-burr any "cut" metal especially when using a drill, IF the metal snags onto the drill bit you will have yourself a Very sharp spinning Razor, you can't pick up sausages with no fingers
Thanks for the tip on sourcing magnet wire. I've been trying to use old microwave transformers and ending up trashing most of the wire because they don't make transformers like they used to.
I remember the crystal radio kits in my younger days. The projects on the now gone electronic mahazines. All the catalogs that sold left over parts from manufacturers like resistors and such. Also buying parts at Radio Shack.
Start with asking yourself what exactly is a diode and what does it do. There's a certain asymmetry every diode should have, and there are many ways of achieving this effect that does not rely on any magical quantum silicon stuff. There were diodes long before silicon semiconductor technology.
Well, I did the opposite once; took a length of wire and rewound a television's yoke! The part was unobtainable, and I really wanted to keep that TV going. It actually worked, but it was no fun doing the winding. I did say "once", didn't I? Never again! lol
Dumb people don't care about pretty much anything :q Until a huge global cataclysm wipes off their toys made by smart people. Then you will come whining to that dude to make you some crappy radio.
The radio waves themselves provide the power. The voltage is too small to run more than a small earphone, so in most radios, an amplifier is used to drive a larger speaker.
So this is something called a crystal radio idk how legitimate this video is but from my understanding that coil he made (the toilet paper roll) is able to pick up frequencies we put in the air and then output them into the speaker. If you use an oscilloscope to measure the frequency peaks on the coil you'd probably be able to see the fm radio stations in your area but again I'm not sure how legit this guy's build is so if you want to find even more about this kind of stuff look up crystal radios
It's only works with AM only (The radio signal is demodulated by the diode), and the headphone has to be a high impedance one Amp doesn't power radio it uses the power carried by the radio waves instead as AlexR2648 said
I made one of these. If I remember right it was a bit different, melted lead and dropped a pinch of sulfur onto the molten lead, making a galena crystal. I was in grade school then, early 60's.
Nice crystal set. It would be better if you narrated it so that people who didn't know what you were doing could learn what you are doing. I like that you use scrap wire and homemade diode.
Just saw this today.. nice video. I used to ground cable for a cable company, and they always told us to ground to cold water just FYI, surprised I don't see it mentioned.
Can you explain why the clear nail polish was used and how it effects the radio? Also, is there any replacement for the polish or is it suitable to not use polish?
I only use it so that the wires lock in place and don't twist. You could use something else that holds them in place. Without something, the wires will twist when you sand the enamel off the wire which will cause them to short in some places.
I built the samilar radio at 73, using a 1N60 diode, a AM ferrite antenna and a VC parallel each other, then, antenna and earth connection as usual circuit, using a crytal high ohm earphone to connect after 1N60 diode. Moving the ferrite and tunning the VC, then finally, it works.
