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Are you afraid that when the big one is dropped,
the electromagnetic pulse will wipe out your diode? Well, this
crystal set may be the answer. Tubes don't get clobbered by those
nasty pulses. I proudly announce to the world the creation of
my one tube diode receiver.
You are now thinking - "Only an idiot would build a diode tube radio".
Well you are certainly correct, this idiot
did build one.
If you have visited my other crystal set pages, you
will notice that many of my sets use the one coil, two capacitor
circuit. That is because it works so well. For more
details, please visit my #12 page.
What is new with this set is the inclusion of a vacuum
tube. This is still a diode receiver as the tube is not powered
for amplification. It could, if you wanted it to as there is a
pentode section to this tube. The 1S5 is a diode detector and
audio amplifier tube. I am using only the diode section. I attempted
using an old TV high voltage rectifier tube, such as a 1G3, but the
reception was very weak. So I settled for the 1S5. You can use
other tubes. I even tried using the control grid as the diode
plate and that worked also.
I use one of my link switches in this design. This type
of switch looks very nice, but you could use a toggle switch and
get the same results. When the switch link is moved towards the
tube, the filament will light and the tube will be doing the
detecting. When the switch is moved to the other thumb nut, then
the diode is doing the work. This is a combination on/off switch
and detector switch.
The coil is wound with 54 turns of
40/44 litz wire with
a tap at 40 turns. This set is designed for use with a crystal
earphone, but a high impedance headphone would also work. Sound
powered phones can be also used, but the resistor should be
removed and a transformer, pot and capacitor must be added. I
will be covering sound powered phones in a future radio.
How does it work? Very nice indeed. The signal is
louder with the 1n34a diode than the tube. A single D cell can
provide many hours of listening pleasure, but the diode operates
in the "Schmarder mode" aka free.
Best wishes and good DX. Dave - N2DS
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