Crystal Radio Crystal Radio Detector Diode Cast in Brass Cup Hematite Granular

Description

Crystal Radio Crystal Radio Diode Cast in Brass Cup
1 piece
Hematite
Crystal Detector-
Granular Hematite
Crystals mounted and Cast in a 13mm" Diameter brass cup
Casting alloy is made from Lead, Tin and Bismuth-Cadmium Free
Experimental Crystals For the Experienced Crystal Radio Enthusiast
Hematite
is a
semiconductors that may possibly need some biasing
(see picture
)
to make the detector more sensitive by adding a forward
bias
voltage that is usually applied using a 1.5V battery and a 50K potentiometer.
FACTS ABOUT OLD SCHOOL CRYSTAL DIODES
Not every contact position on the crystal will perform, so fiddling with the ‘cat's whisker’ to find a sweet spot does take patience and some acquired skill.
Cat Whisker:
The "cat whisker", a springy piece of thin metal wire, formed the metal side of the junction. Phosphor bronze wire of about 30 gauge was commonly used because it had the right amount of springiness.
Cat whisker detector:
It consisted of a pea-size piece of crystalline mineral in a metal holder, with its surface touched by a fine metal wire or needle (the "cat whisker"). The contact between the tip of the wire and the surface of the crystal formed a crude unstable point-contact metal–semiconductor junction, forming a diode. The wire whisker is the anode, and the crystal is the cathode; current can flow from the wire into the crystal but not in the other direction.
Having a lot of patience and a steady hand are needed when you listen with a piece of the rock. But this can also be very rewarding when you can hear the first station using a cats whisker detector.