How a Crystal Radio Works
1,192,776
Published 2012-08-30
We start with a demonstration of all the parts in action, showing how the radio waves interact with the antenna and antenna coil to produce a fluctuating magnetic field, which induces electron flow in the tuning coil, which works with the tuning capacitor, which is followed by the diode and crystal earpiece. We talk about why a leaky germanium diode is needed with this particular circuit or how a bypass resistor can be used instead.
That's followed by how the tuning is done using a tuning coil in parallel with a tuning capacitor, which together are tuned to a resonant frequency the same as the radio frequency by adjusting the coil's inductance and the capacitor's capacitance.
Then we show how a radio wave is formed from a microphone's audio wave using amplitude modulation (AM). This then shows how the diode is necessary for converting the radio wave back to an audio wave for use by the earpiece or speaker.
Next we discuss selectivity versus sensitivity and why a separate antenna coil is used.
An finally we show a few other crystal radio circuits.
Thanks to the following for reviewing development versions of this video:
Slovenija12345 of youtube.com/user/Slovenija12345
and
Charles Wenzel of www.techlib.com/electronics/crystal.html
See also...
How to Make/Build a Crystal Radio video, the radio explained in this video:
• How to Make/Build a Crystal Radio
Crystal Radio Troubleshooting and Tips video:
• Crystal Radio Troubleshooting and Tips
How to Make an Amplifier for a Crystal Radio Earpiece video:
• How to Make Amplifier for Crystal Rad...
Make a Crystal Radio Coil with Taps video:
• Make a Crystal Radio Coil with Taps
There's also a crystal radio page on my website:
rimstar.org/equip/crystal_radios.htm
3D modelling and 3D animation done using Blender 2.63.
To follow me on Twitter:
twitter.com/RimStarz
rimstar.org/
All Comments (21)
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Today was my birthday. I’m 75. I started listening to crystal radios when I was 9 or 10 years old. I became an mechanical engineer. This video gave the first practical understanding of how a crystal radio works. What a great birthday present. Thanks. You know your audience.
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Many years later it's still the best explanation of how a crystal radio works on Youtube.
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Yeah, that's a deliberate requirement I set when making all my explanations, that I show the thing working at as low level as practically possible so that there's little left to the imagination. Words and static diagrams play a part, but seeing the electrons, electromagnetic fields, radio waves, heat flow, ... makes how it works blatantly clear.
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The radio gets its power from the radio waves themselves. No batteries or other power source is required.
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Finally a video that I can wrap my head around to understand Radio. A Million thumbs up. Thank you for taking the time to make such excellent tutorials.
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Thank you! I finally understand how a crystal radio works after 50 years!
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This is the BEST crystal radio explaination I have ever seen. Outstanding in all categories...!
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The diode is for converting the radio wave back to the original audio wave, as is said at 10:20 in the video and explained in the section before that. For the antenna, I showed that in my How to Make a Crystal Radio video. I just used one of more 15 foot longs wires in parallel, connected where the antenna goes in the circuit. Depending on how close you are to radio stations you may need longer. 15 feet is actually pretty short.
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UTTERLY BRILLIANT PRESENTATION!! You sir should win the Nobel Prize for the best explanation and presentation ever.
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This is the first explanation I have ever seen that made clear the basis of radio. All others seem to be interested in displays of genius. You sir have a new subscriber.
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You're welcome! It was a pleasure being able to make this one, mostly because to do it I had to learn the pieces I didn't know. I'm glad you liked it. Thanks!
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When I was six or seven year old the farther of my friend made a crystal set for his daughter, some times I was aloud to listen and I can remember how amazing it was to me, until today I had no idea how it worked. Thank you for making this video.
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I made my first crystal radio around 1960. This is the first time I have heard a good explanation of how it worked!
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Did you know that you're the only one with a video that talks about how radio waves interact with radios? There is not a single video explaining exactly how radios word with detail.
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For 27 years I've been looking for this video. Thank you sir. Thank you. You have enlightened my brain!
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WOW... I made my first crystal radio back in 1972 and it`s the first time I really understand what the diode is there for. No one ever explained it the way You did... FANTASTIC... I`m gonna build one again and use my DSO to look at the different frequencies in the circuit. Thanks a lot here from Denmark!
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I've never seen such a wonderful explanation in my entire life. Big congratulation from Italy. Answered any of my questions and explained a lot more.
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We've continued this in private messages for more room but for the benefit of others, larger diameter plays a part when you get into loop antenna coils. Those are crystal radios where a large diameter coil (1 1/2 feet in diameter for example) is used as both the coil and the antenna. You can see one of these in my "Portable Crystal Radio using Loop Antenna and Pizza Box" video.
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Thank you for publishing the first description of how a AM radio works that I can truly understand. Much appreciated.
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Thanks for this video. When I was about 14, my parents bought me a radio-shack experiment kit for Christmas. The crystal radio design worked and my mother was amazed. This was the only time she ever seemed impressed with me. I was so moved by her reaction that i later got a BS degree in electrical engineering. While i did take the class on radio theory, I don't recall them explaining what the diode was for. After these 40 years, I might have just forgotten but it is certainly a treat to hear that old circuit explained so well as your video does.
