28 Nov
2009
28 Nov
'09
11:53 a.m.
On 28 Nov 2009 at 18:29, Tony Duell wrote:
THey are not hard to find. I am sure they turn up on
E-bay. Or grab a
junker AA5 radio and remocve the rtuning capactior, If it's too high a
capacitance, rip off some of the moving plates (seriously).
I'll admit that finding SLF, SLC or SLW air variables nowadays can be
very difficult. But they were never that common even in the heydey
of tube radios.
I recall making a "crystal set" using nothing more than a razor
blade, safety pin, and pencil "lead" and a tuning coil (and of
course, a set of high-impedance headphones). You can build a small
capacitor using nothing more than waxed paper and aluminum foil.
The web contains lots of sites dedicated to the resurrection of some
old practice or the other. There are instructions on how to build
electrolytic rectifiers (used as "B" battery substitutes for early
transmitters), all manner of "crystal" sets, including sources for
minerals, even early solid state negative resistance devices (long
before the junction transistor).
There's even a Yahoo group dedicated to construction of regenerative
radio receivers.
It's noteworthy that much hobbyist radio work came into flower during
the darker days of the Great Depression, when money was very scarce.
Information on tube construction is perhaps more readily available
today thanks to the internet than at any other time.
--Chuck