3 ms·

I’m second grade I brought one in for show and tell that I had made. The teacher was absolutely righteously confused, but seeing it didn’t plug into the wall o

I’m second grade I brought one in for show and tell that I had made. The teacher was absolutely righteously confused, but seeing it didn’t plug into the wall or take batteries, allowed it. A team is kids held up the antenna so others could take a turn listening and tuning and it was a pretty big hit. I used of the shelf transistors from radio shack and the design was out of a electrical engineering book I had read over the summer before. My dad is a geologist, but be helped me learn to solder and make it look nice. I wish i had pictures of all this. I owe a huge amount of my success to my teacher and my dad for moments like this.

drivers99 3y ago
Every crystal radio I’ve tried to build has not made any sound. I’ve tried a Radio Shack kit (which should just work) and tried building it from scratch (making my own coils and so on) from online plans. Perhaps I’ll give it another shot though.
- wrycoder 3y ago
  You need high impedance headphones, which are uncommon these days. Try a high impedance portable speaker instead of headphones.
  - nonrandomstring 3y ago
    The "crystal" in the name actually refers to two components both of which are as you say of extraordinary high impedance, about 10M Ohms. The harder part to get your hands on is the "Crystal ear-piece" These were popular in hearing aids circa 1960. They are piezo transducers with a diaphragm in a small housing. Perhaps , as you say, the next best modern component would be a piezo loudspeaker, but check its impedance is several M Ohms. The second "crystal" in the set is a diode. Some designs just use a germanium diode like OA81 , but the authentic design that replicates the POW radios built in camps uses a coiled brass wire and a piece of "coke" (being a form of coal). The coke nugget contains silicon and similar elements. When the springy brass wire touches it just right it forms a semiconductor junction. Getting that to work along with an improvised plate capacitor is pushing luck to the limit, so I am not surprised many kids never get this to work. If anything it's an exercise in tenacity, patience and faith it might be possible. I did actually get this to work for about 10 minutes in 1975 when BBC World Service blasted out on "long wave". Another problem is the disappearance of high power AM transmitters. So you need to be lucky and live in the right place for this to work nowadays.
    - drivers99 3y ago
      > If anything it's an exercise in tenacity, patience and faith it might be possible. The problem I realized last time was that I didn't have any way to troubleshoot it that I could figure out. I now have an oscilloscope but I'm not sure if that will help. > Another problem is the disappearance of high power AM transmitters I'm about 10 miles away from a 50,000 watt station (850 KOA[1]) so that should work. [1] https://en.wikipedia.org/wiki/KOA_(AM) https://en.wikipedia.org/wiki/KOA_(AM) I used to listen to this station from other states at night.
  - drivers99 3y ago
    I used the earpiece that came with the Radio Shack kit which is the type you mentioned. If I can't find one, I'll keep that in mind.

drivers99 3y ago

Every crystal radio I’ve tried to build has not made any sound. I’ve tried a Radio Shack kit (which should just work) and tried building it from scratch (making my own coils and so on) from online plans. Perhaps I’ll give it another shot though.

wrycoder 3y ago
You need high impedance headphones, which are uncommon these days. Try a high impedance portable speaker instead of headphones.
- nonrandomstring 3y ago
  The "crystal" in the name actually refers to two components both of which are as you say of extraordinary high impedance, about 10M Ohms. The harder part to get your hands on is the "Crystal ear-piece" These were popular in hearing aids circa 1960. They are piezo transducers with a diaphragm in a small housing. Perhaps , as you say, the next best modern component would be a piezo loudspeaker, but check its impedance is several M Ohms. The second "crystal" in the set is a diode. Some designs just use a germanium diode like OA81 , but the authentic design that replicates the POW radios built in camps uses a coiled brass wire and a piece of "coke" (being a form of coal). The coke nugget contains silicon and similar elements. When the springy brass wire touches it just right it forms a semiconductor junction. Getting that to work along with an improvised plate capacitor is pushing luck to the limit, so I am not surprised many kids never get this to work. If anything it's an exercise in tenacity, patience and faith it might be possible. I did actually get this to work for about 10 minutes in 1975 when BBC World Service blasted out on "long wave". Another problem is the disappearance of high power AM transmitters. So you need to be lucky and live in the right place for this to work nowadays.
  - drivers99 3y ago
    > If anything it's an exercise in tenacity, patience and faith it might be possible. The problem I realized last time was that I didn't have any way to troubleshoot it that I could figure out. I now have an oscilloscope but I'm not sure if that will help. > Another problem is the disappearance of high power AM transmitters I'm about 10 miles away from a 50,000 watt station (850 KOA[1]) so that should work. [1] https://en.wikipedia.org/wiki/KOA_(AM) https://en.wikipedia.org/wiki/KOA_(AM) I used to listen to this station from other states at night.
- drivers99 3y ago
  I used the earpiece that came with the Radio Shack kit which is the type you mentioned. If I can't find one, I'll keep that in mind.