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Hi there. Here is a pretty simple crystal set project that
you and the kids can build before any of you lose your concentration. The tuned
circuit is based on the
Tuggle Tuner that is popular in
high performance crystal sets. This set is like my
#12 set too. Yes, I know this is starting to sound like
a mutt crystal set, but it really works quite well.
The wood base is made from the top to the box that became
my #8 Octoset. I hate to waste anything. The variable
capacitor is a multi section unit. Just the two larger capacitors are used
here. The coil is wound with 40/44 litz wire on an
AOL cd spider coil. The set is quite
attractive with the knurled brass thumb nuts.
This radio has the ease of tuning that my #13
has but works better. The ganged capacitor boosts this set to the medium performance set.
Use the parts you have around. If you have an old radio tuning capacitor with
a 365 pf antenna section and a 140 pf oscillator section, go ahead and use
it. Put the smaller section directly across the coil.
The coil is not tapped on this radio. The best performance is
achieved with an audio transformer
with around a 100k ohm primary impedance.
If you have one of these, take out the 47k resistor and replace it with a
100 - 200 pf fixed capacitor. Do the same if you want to use high impedance
headphones without a transformer. You can, in this situation, move the
diode to a tapped position on the coil. About ten turns down from the
top would be around right. Leave the circuit as is for a crystal earphone.
I really like how this set looks and I hope you do too.
Best wishes ~ Dave
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