[CW] OT: foxhole radios

Tue Oct 25 09:30:51 EDT 2022

https://store.scitoys.com/simple-crystal-radio-kit.html

73
DR

On Tue, Oct 25, 2022, 12:01 AM Steve WD8DAS via CW <cw at mailman.qth.net>
wrote:

>
> Here's a website with lots of good crystal set info...
>
> http://www.midnightscience.com/
>
>
>
> Steve WD8DAS
>
> sbjohnston at aol.com
> http://www.wd8das.net/
> http://af4k-crystals.com
> --------------------------------------------------------------------
> Radio is your best entertainment value.
> --------------------------------------------------------------------
>
>
> -----Original Message-----
> From: Steve WD8DAS via CW <cw at mailman.qth.net>
> To: cw at mailman.qth.net <cw at mailman.qth.net>
> Sent: Mon, Oct 24, 2022 10:59 pm
> Subject: Re: [CW] OT: foxhole radios
>
>
> 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 at aol.com
> http://www.wd8das.net/
> http://af4k-crystals.com
> --------------------------------------------------------------------
> Radio is your best entertainment value.
> --------------------------------------------------------------------
>
>
> -----Original Message-----
> From: Steve WD8DAS via CW <cw at mailman.qth.net>
> To: cw at mailman.qth.net <cw at 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 at aol.com
> http://www.wd8das.net/
> http://af4k-crystals.com
> --------------------------------------------------------------------
> Radio is your best entertainment value.
> --------------------------------------------------------------------
>
>
> -----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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