Spider Coil Form
|I built this
radio for a friend of the Family. A great guy who gave me an
incredible amount of parts and material for Kite building. I
used my own design for a spider coil and wound about 65 turns of 24
gauge magnet wire. This gave
me about 330 uH of inductance to work with. I used a simpler
capacitor that can be bought here as opposed to a variable air capacitor.
Shorting the two ends this capacitor will give you over 240
pF, enough to tune the whole AM band. There is a 47k resistor in parallel with the
ear piece and a standard 1N34 Germanium diode.
For the actual form and front piece I used a small sheet of
Lexan; it's durable and virtually indestructible. This set
has a high Q value and has great
selectability. This is due to the loose wound theory.
If the wire is not close wound there is less capacitance
built up, thus greater selectivity. If anyone is interested
in the exact measurements or is interested in making a similar radio,
feel free to email
I know crystal sets have been around for a
loooong time. I'm sure similar radios have been built and I
do not claim that this is an *original*.