When I lived in Africa, Galena was used in the crystal sets which some of my
friends and I built during the very early 1940s. Galena could be found in
some outcrops of rock, many of which were present in our garden. Finding
the "sweet" spot for the cats whisker could be difficult.
Although at home in Nyasaland (now 7Q7) the crystal sets could not receive
any signals (no local BC stations), they were responsible for my obtaining a
ham licence in 1946. Around 1941 a friend and I used to practice "morse"
using a buzzer. We soon discovered that when the key was closed, a raspy
buzzing sound could also be heard from a crystal set placed near the buzzer.
One discovery led to another, leading to two-way buzzer contacts without
interconnecting wires over distances of tens of feet. All came to a rapid
halt when the source of strange noises on the family's SW BC receiver was
found to be two cub scouts practicing morse!
73,
Geoff
LX2AO
On July 25, 2013 at 9:52 AM, David Gilbert wrote:
Actually, I'm pretty sure the crystal set you are referring to used a
piece of galena (a lead sulphide compound), not germanium (and not
geranium, which is a flower). Early crystal sets used a piece of springy
wire called a "cat whisker" to contact the galena at a sometimes
difficult-to-locate crystal, in essence forming a crude point contact
(i.e., Schottky) diode. The crystals are small but naturally occurring in
the galena. My dad had such a set and I remember using it when I was
about six or seven years old (60 years ago for me), but by that time
actual germanium diodes were available and my first "real" radio used one
of those.
73,
Dave AB7E
On 7/25/2013 12:22 AM, Chuck Smallhouse wrote:
My first experience hearing local AM stations was using an actual chunk
of geranium crystal mounted in a blob of lead, that you'd traded some of
your best agate marbles for, You used the point of a fine safety pin to
scratch around on that chunk of geranium to find the sweat spot, where
the station (s) came in the best into your headphones. It didn't seem to
be the same spot night after night ! You tried to use the longest wire
that you could sneak out your window and up to near the top of the
tallest tree in your back yard.
Later if you wanted to separate KVOA (1290) ad KTUC (1400), here in
Tucson, you had to wind a big coil on an empty round oatmeal box, and try
and tune it with a variable capacitor that you'd "rescued" from a defunct
radio. This was all mounted on a "bread board", generally a short
section of a 1x 6" or a 1x 8"pine or redwood board. Terminal points were
metal screws into the board (preferably brass) that the wires were
wrapped around !
Gee, that was well over 70 years ago ! Time sure flies when you are
having fun !
Chuck,. W7CS
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