For those who are asking about the loop crystal set I mentioned, here's a description of the design. 

http://www.wd8das.net/CigarBoxCrystalSet.pdf

It involves winding magnet wire around the perimeter of a cigar box as both the tuning inductamce and the antenna, and mounting the other components into the box.  It worked pretty well with any external antenna or ground.  It was better with a long wire and ground attached, but did work for city-grade signals with just the loop.


Steve WD8DAS

sbjohnston@aol.com
http://www.wd8das.net/
http://af4k-crystals.com
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Radio is your best entertainment value.
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-----Original Message-----
From: Steve WD8DAS via CW <cw@mailman.qth.net>
To: cw@mailman.qth.net <cw@mailman.qth.net>
Sent: Mon, Oct 24, 2022 5:23 pm
Subject: Re: [CW] OT: foxhole radios

For an unpowered "crystal set" AM radio receiver you only need a few parts if you are in a reasonably strong signal area.  I've made them with a loop antenna and for use with long wire antennas.

As I understand it, the old "blued" razor blades and a pencil lead (graphite) formed a semiconductor at the point they touched.  Modern razor blades do not show this effect so that will likely be a bust.

The 1N34A diode is a factory-made germanium crystal and cat-whisker wire assembly sealed into a small glass tube.  It is a much better practical radio detector than the old hand-crafted detectors. 

You can still purchase 1N34A diodes new from parts suppliers.  Even Amazon has them...

https://www.amazon.com/BOJACK-Germanium-65Volt-Electronic-Silicon/dp/B07Q4J9WMX/

The tuning coil and capacitor are usually connected in parallel and the combination is connected between the long wire antenna and a good earth ground.  The coil and capacitor can be either purchased or hand-crafted.  It looks like Amazon has some.  The diode detector goes in series with the headphones which together are connected across the coil and capacitor.

The audio output needs to feed into high-impedance earphone or headphones, which can be a challenge to find today.  I see that Amazon has one, though...

https://www.amazon.com/Piezoelectric-Impedance-Transistor-Electronics-Sensitivity/dp/B071JWPTT9/



 

Steve WD8DAS

sbjohnston@aol.com
http://www.wd8das.net/
http://af4k-crystals.com
--------------------------------------------------------------------
Radio is your best entertainment value.
--------------------------------------------------------------------


-----Original Message-----
From: Joseph L. Pontek Sr. <v31jp1957@gmail.com>
To: cw@mailman.qth.net
Sent: Mon, Oct 24, 2022 8:52 am
Subject: Re: [CW] OT: foxhole radios

The fox hole radio was a very basic crystal radio. My first radio
was a crystal radio. It had a crystal in a glob of lead (solder) and
what they called, a cats whisker. It was a spring loaded wire that
you could move around on the crystal until you found a "hot spot."
When I talked to my Uncle Stan, a WW II vet, he told me about
using the razor blades. I think in a Boys Life magazine, I read
about that method. Both were very finicky to get to work. Then
my Great Uncle Vern gave me a little diode, maybe a 1N34A
or the like. Worked right off!
The diode does not generate electricity, it simply rectifies RF
that is picked up via a wire (antenna) and against a ground.
I made tuning coils by wrapping enamel insulated wire on
paper tubes, toilet paper tubes, oat meal boxes, etc. I sanded
the insulation with sand paper and made a sliding contact
the shorted out part of the coil, ie, tuned it. It was very broad
banded, so I heard two local A.M. broadcast stations at the same
time. I used a pair of surplus crystal earphones.
If you want to supply some one the needed materials, I would
assemble some diodes, like 1N34A, 1N914, or such, enameled
copper wire for the coil, earphones, hook up wire and, maybe,
fan-stock clips, some hardware, like screws and nuts and some
antenna wire.
My first ones were made on just a piece of wood. They got me into
electronics, ham radio and career in electronics 70+ years ago.
I used to teach ham radio classes at the Michigan School for the
Blind, so I understand the handicap fairly well.
I hope this helps.
73, Joe, K8JP/K5

On 10/24/2022 8:05 AM, Jude DaShiell wrote:
Hi David,
That's all the information I got on foxhole radios some of them used
graphite pencils and razor blades.  Two different kinds of metal in
contact certainly would produce electricity as illustrated when a N.A.S.A.
contractor figured out the specification writers requiring only one kind
of metal for those Mars Rovers was wrong and used two different metals.
The batteries kept recharging and N.A.S.A. got lots more data back on Mars
than they expected thanks to that contractor correcting that mistake.
-- 
Regards, Joe, K8JP/V31JP, Ronnie, Martin & Sidney Pontek
175 Diamond Loch Rd., Apt. 5
Gilmer, TX 75644-9374
U.S.A.
903-204-2318 (My TX cellular)

Member FOC-1743 Feb 2001, QCWA-LM21894, OOTC-4607, American Legion, A1OP, CFO 1055, SKCC-3171T, NAQCC-5798, Flying Pig-2819, FISTS-7625CC951, A1C-2299, SOC 1075, 10-10 22977, PG1915841, CW Rag chewers #21,
Facebook: Joe Pontek
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