[CW] OT: foxhole radios

Mon Oct 24 18:23:06 EDT 2022

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 at aol.com
http://www.wd8das.net/http://af4k-crystals.com
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-----Original Message-----
From: Joseph L. Pontek Sr. <v31jp1957 at gmail.com>
To: cw at 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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