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Author Topic: Seeking old sources of radio crystals  (Read 5224 times)
AK0B
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Posts: 30




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« on: September 26, 2014, 08:21:51 PM »

I am interested in experimenting with old minerals (radio crystals for receiving)

i.e. Carborundum      Is this available as Lely crystals ?

Looking for a rock shop, etc. that might be a source of those old minerals from yesteryear.

Thanks, Stan AK0B    w9ifz@yahoo.com
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KA4POL
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« Reply #1 on: September 26, 2014, 09:55:17 PM »

You could get it from industry, at least worth a try: http://www.carborundumindustrial.com/CarborundumAboutUs.aspx
Another direct source: http://www.nitride-crystals.com/Lely-Crystals.htm
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KB1WSY
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« Reply #2 on: September 27, 2014, 04:56:28 AM »

A couple of years ago I started searching for sources of crystals and accessories.

The main issue is using the right search term.

For crystals, try the word "galena."

For crystal holders, try "cat's whiskers" or just the word "whisker" in combination with radio terms. For instance, "crystal detector" or "galena detector."

You can homebrew your own cat's whisker crystal holder/detector. I don't have the document references to hand, but you should be able to find them using those terms. Or you can just buy one; eBay is one source, just search for "galena whisker" or "crystal detector."



There's even someone on eBay offering a complete experimenter's kit, including samples of galena and iron pyrite, for about $24 "buy it now" including shipping (http://www.ebay.com/itm/Crystal-Radio-Experimenters-Detector-Kit-/251428547849?pt=LH_DefaultDomain_0&hash=item3a8a4f2d09).

73 de Martin, KB1WSY
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W1JKA
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« Reply #3 on: September 27, 2014, 05:18:29 AM »

 Or if your REALLY into home brewing you can grow your own, just Google "New Developments in Crystal Growth Research" Showing furnace construction and other needed info. Wink
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G3RZP
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« Reply #4 on: September 27, 2014, 06:07:52 AM »

Back in the 'good old days', the impecunious would get some of the lead foil that father's pipe tobacco had wrapped round it and fold it around some flowers of sulphur: this was placed on a brick.  A blow torch was used to set fire to the sulphur, and when everything had cooled, there was, if you got the proportions about right, a crystal of galena!

'Fool's Gold' or iron pyrites was used, too. Carborundum needs a fine steel point on the cat's whisker and is best biased with DC and is a better rectifier when hot - up to 400 deg C! Galena needs a very light touch with a copper cats whisker.
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KB1WSY
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« Reply #5 on: September 27, 2014, 04:34:09 PM »

Hey Stan/AK0B, I'm sure we'd really appreciate hearing how your experiments turn out.

I for one have been toying with this concept for a while. It's the ultimate homebrewing:
--a rock
--a whisker (razor blade, pencil lead, whatever)

It would be cool to homebrew the earpiece as well!

G3RZP speaks with the voice of experience, thank  you for the advice, Peter.

Too bad there's no way we could use a crystal radio for a ham QSO -- or could we?? (I mean a real QSO over at least several miles, not just a very local experiment.) We have strict rules for our transmitters, but our receivers can be as rudimentary as we like!!!

Edited to add: as far as I can tell the technological progression was as follows.

The first detector was Heinrich Hertz's spark gap. That's right, he detected a microscopic spark between two contacts across a darkened lecture hall. He could see it with the naked eye, even though it existed for only a tiny fraction of a second.

The second detector was the "coherer" which was basically iron filings in a glass tube.

The third detector was the "crystal" that we have been discussing.

The fourth detector was the vacuum tube rectifier that we are familiar with.

73 de Martin, KB1WSY
« Last Edit: September 27, 2014, 04:40:17 PM by KB1WSY » Logged
WB6BYU
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Posts: 13341




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« Reply #6 on: September 27, 2014, 04:40:59 PM »

It should detect an AM signal just fine.   With a bit of negative resistance and a battery you might get it
to oscillate, in which case it would receive CW.

When someone scoffed at the idea of a crystal set picking up international SW broadcasts, a friend added
a diode detector and headphones to a Johnson Matchbox and picked up a number of stations using a
wire antenna.

You probably could make a QSO on 160m AM with one.  By the time you get up to 20m your bandwidth
would be pretty wide and there would be a lot of QRM.
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AK0B
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« Reply #7 on: September 27, 2014, 09:52:50 PM »

Thanks fellows for your suggestions. Several are very very good and I will follow up on them. 
Stan AK0B
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G3RZP
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« Reply #8 on: September 28, 2014, 03:16:19 AM »

My 1924 3 volume 'Harmsworth's Wireless Encyclopedia' has a lot of info that can be dug out if you need it.
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K1ZJH
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« Reply #9 on: September 29, 2014, 07:07:21 PM »

I have several carborundum detectors.  They all seem to work quite well without the recommended DC bias.  A few of my Carborundum mounts have a rheostat and a holder for a dry cell.  You might try looking at the Modern Radio Labs website to see what ores they might carry.  Carborundum is a man made product.

Pete
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KD0REQ
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« Reply #10 on: September 30, 2014, 10:42:45 AM »

Carborundum is silicon carbide.  for that matter, you could try putting a cat whisker on a tipped Skilsaw blade.  cheapest, most availiable source of material.  it's glued onto the saw blades, however, so you probably need two whiskers, or try cracking it off and potting in lead.
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KB4QAA
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« Reply #11 on: September 30, 2014, 06:07:18 PM »

http://www.midnightscience.com/catalog5.html

"The Xtal Set Society" has all the parts needed for sets, including raw and mounted Galena crystals.

I believe this is the retirement project of Phil Anderson W0XI, founder of Kantronics.
« Last Edit: September 30, 2014, 06:12:13 PM by KB4QAA » Logged
N3QE
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« Reply #12 on: October 01, 2014, 08:07:46 AM »

Too bad there's no way we could use a crystal radio for a ham QSO -- or could we?? (I mean a real QSO over at least several miles, not just a very local experiment.) We have strict rules for our transmitters, but our receivers can be as rudimentary as we like!!!

AM would be easy.

SSB will make donald-duck type sounds in a crystal AM detector and with some practice you can kinda hear the words in it.

The crystal detector is detecting CW as well, but turning it into a lowish on-off DC voltage rather than an audio tone. With the old-timey high impedance metal-plate-diaphragm headphones you can actually hear the "on" and "off" transitions from morse as different kinds of clicks vs clacks, and just like American Morse was used on telegraph sounders, you can do Continental Morse the same way.
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AA4HA
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« Reply #13 on: October 03, 2014, 12:09:12 PM »

You can make a spark-gap transmitter out of an old relay. Just don't expect it to last for more than a few minutes before the contacts melt.

Definitely one that we are not allowed to do any more, unless you define your transmitting frequency as "less than 20 meters".  Wink
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
KD0REQ
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Posts: 972




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« Reply #14 on: October 03, 2014, 12:41:51 PM »

or define the bandwidth as "yes"
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