Uploaded December 2024 | Updated September 2026, 2 weeks ago

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Another experiment to see why the bobbin windings in a capacitively tuned crystal radio produced almost no sound.

Another experiment to see why the bobbin windings in a capacitively tuned crystal radio produced almost no sound.

We are starting with a known, working coil and 1 by 1 varying the parameters that were changed with the bobbin coils:
-- Wire diameter
++ Winding type (straight 1 layer vs. multi-layer scatter) (this video)
-- Core size


KNOWN STANDARD COIL:
- Wire size big: 0.81mm (20 AWG)(Done/standard) Straight wound
- Core: 42 mm (1.65") PVC plastic
- Inductance total: 205 uH (Measured)
- Taps: 0T, 20T, 30T, 80T


EXPERIMENTAL COIL (SCATTER WOUND):
- Wire size fine: 0.227mm (31 AWG)(Done/standard) Scatter wound
- Core: 42 mm (1.65") PVC plastic
- Inductance total: 205 uH (Calculated)(220 uH measured after adjustment)
At 9.36 meters of wire, the original inductance was 360 uH.
1.8 meters of wire was removed to achieve 220 uH.
- Taps: 0T, 10T, 15T, 40T Total: 65T
- 10/65 = 0.154; 15/65 = 0.2308; 40/65 = 0.6154
- 10/65 = 0.154 (* 9.36m = 1.44m); 15/65 = 0.2308 (* 9.36m = 2.16m); 40/65 = 0.6154 (* 9.36m = 5.76m)



BOBBIN COIL (capacitively tuned version):
- Wire size fine: 0.227mm (31 AWG)(Done/standard) Multi-Layer Scatter Wound
- Core: 8 mm (1.65") plastic
- Inductance total: 219 uH
- Taps: 0T, 10T, 15T, 40T


RELATED VIDEOS:
Crystal Radio--The Bobbin Inductors Fail. But WHY? 2/2
youtu.be/iH66WckUzFE

Crystal Radio--No More Small Core Inductors??? Maybe. 1/2
youtu.be/CJlAwvE5p7g

Crystal Radio--Cheap & Easy Inductor From Sewing Machine Bobbin
youtu.be/ecuhAiBYJzs

1 Capacitor Crystal Radio--No More Variable Capacitor Designs? (4K)
youtu.be/0AvTO588SyU