[CW] OT: foxhole radios

Mon Oct 24 21:40:40 EDT 2022

The semiconductor is iron oxide.  Modern blades are usually stainless steel.  One can make a detector by crossing the edges of two rusty blades.   Sent from my Galaxy
-------- Original message --------From: "D.J.J. Ring, Jr." <n1ea at arrl.net> Date: 10/24/22  6:24 PM  (GMT-08:00) To: sbjohnston at aol.com, CW Reflector <cw at mailman.qth.net> Subject: Re: [CW] OT: foxhole radios Here is a newer model that says it is more reliable than "other" such units because this one has soldered connections.https://www.amazon.com/Piezoelectric-Impedance-Ceramic-Crystal-Radios/dp/B09MZML96L/73DROn Mon, Oct 24, 2022 at 6:23 PM Steve WD8DAS via CW <cw at mailman.qth.net> wrote:

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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Radio is your best entertainment value.

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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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