I've wasted a lot of time and money building single variable capacitor crystal radios. They just don't work. If this one does not work, it's the last one I'm going to build. I'm done with them!
I found this design on the internet. It's from the 1950s, rather late in the game (many were from the 1920s).
MATERIALS
- 1 x 1n34a diode
- Board (Mine is 18cm x 12cm)
- 1.25" (1.65" actual) PVC pipe (42mm) x 140 mm long
- 20 gauge wire (0.81mm)
- 16 brass or stainless screws
- 10 brass washers
- 2 pillow blocks (wood or plastic)
- 1 10-365 pF air tune capacitor
- 1 bracket for capacitor
- 2 Fahnestock clips
- 1 resistor 10k-40k ohms
- 1 crystal earphone (piezoelectric)
3D Printable Pillow Blocks: https://www.thingiverse.com/thing:6431698
3D Printable 360 pF Variable Capacitor Mounts (2 types): https://www.thingiverse.com/thing:6431705
TOOLS
- Screw driver
- Knife
- Sandpaper (small piece, fine)
- Saw, if you do not have the wood & tube already cut
- Hand drill for screw holes
- (Optional) Soldering iron, solder
ANTENNA & GROUND
- Antenna are just a long piece of wire (I use scrap wire from old transformers). The longer the better.
- Try different lengths and orientations (vertical, horizontal)
- A good ground helps. A wire to a ground rod is good. Metal water pipes also work well.
NOTES:
- The resistor is necessary to get the best sound from these "new" crystal earphones. The new ones are piezoelectric and have lots of capacitance. Without the resistor the charge builds up then discharges so you get constant "static" sounds. The resistor bleeds off charge so you get louder, and much clearer sound.
WARNINGS:
- Never connect radio to any source of power. Not house current, nor batteries, nothing!
- Never use the radio during lightning storms.
- Never run an antenna over or near power lines.
- Disconnect antenna and put lead outside when not in use.
- Never ground to electrical items, plugs or similar.
- If you don't know, don't do it.
OSCILLOSCOPE USED:
$25 Color Oscilloscope! The Incredible DSO138 (4K) https://youtu.be/I5jvzTOeHKc
Using The $25 DSO138 Oscilloscope - Joule Thief & Freq Generator (4K) https://youtu.be/6og4H4boWVo
INTERESTING LINKS
Knob For Variable Capacitor & Similar (D & Round Shaft Versions) https://www.thingiverse.com/thing:6337332
- Knobs for capacitor tuned crystal radio. https://www.thingiverse.com/thing:6191252
- Air Core: http://www.circuits.dk/single-layer-air-core-inductor-calculator/
OTHER CRYSTAL RADIO VIDEOS
- Popular Crystal Radio Design That Does Not Work https://www.youtube.com/watch?v=i2PITPUg2vI&t=2s
- World's Simplest (Crystal) Radio https://www.youtube.com/watch?v=GdvKDFz9Xi4&t=27s
- Good Crystal Radio Connection Points https://youtu.be/G3qjrReHR1k
- My Crystal Radio Does NOT Work (FIXES for common problems) https://youtu.be/kCxQ8iPQx4s
- Crystal Radio Fake 1N34A Diodes! Easy Test (4K) https://youtu.be/H8XlZ7Mry4M
- Crystal Radio DIY Cat Whisker--Wood, Brass, Stainless (4K) https://youtu.be/PQ0clWe8NGU
- Crystal Radio Cat Whisker--Super Upgrade! https://youtu.be/vNrXYt-JoFI
- PSA: Crystal Radio Coil--Bad Plastic Pipe Pt 3--Type That DOES NOT Work! https://youtu.be/cdZWKh7mzGs
- Popular Crystal Radio Design That's a Waste of Time - And Why https://youtu.be/r9Onub2Xpzc
- Crystal Radio, TV, Oscilloscope, Etc Knobs 3D Print https://youtu.be/6B-DouUIBsY
- Crystal Radio 3D Printable Parts (4K) https://youtu.be/BQNaMuYoeKQ
- Connect DC Amplifier to Crystal Radio https://www.youtube.com/watch?v=HOw3yDFXXN4&t=9s
- Crystal Radio, Capacitive Tuning - WORKS GREAT! https://youtu.be/VJ80Nm9KSkE