1901: Semiconductor rectifiers patented as “cat's whisker” detectors

https://www.computerhistory.org/siliconengine/semiconductor-rectifiers-patented-as-cats-whisker-detectors/

by indus • 3 years ago

62 38 3 years ago

computerhistory.org

archo2• 3 years ago

Hence the Crystal Set was born.

indus• 3 years ago

It's remarkable to see how crystal rectifiers played a crucial role in early radio sets--without external power.

msla2• 3 years ago

without external power.

The radio transmitter is the external power. The crystal set is a way to grab a tiny amount of the electrical power being paid for by whatever entity is running the transmitter. You can play around with the inverse square law and figure out how little power the set is grabbing, but it's working on the basis of what it does grab.

quickthrower2• 3 years ago

I made one in one of those electronic kits in the 80s that had springs you poked wires into. Pretty cool to pick up “the station” on am (there was no tuning I think loudest won)

Aloha• 3 years ago

Crystal sets are remarkably sensitive, though early radios were not very selective, which describes most of the issues with the first 20 years of radio.

kpgraham• 3 years ago

It used to be possible to make a radio receiver out of a diaper pin and a blue razor blade. The coating on the blade acted like a crystal. You needed a cheap pair of headphones or a tiny transistor radio speaker. I made one when I was a kid, and I could clearly pick up 77 ABC in New York City from 50 miles away. Razor blades aren't blue anymore, but there must be other things that work.

Kirby64• 3 years ago

Fun fact, the blueing that creates that effect is literally just steel blue. You can accomplish the same thing by torching a razor blade until it glows then letting it cool.

userbinator2• 3 years ago

It still is, and I hope it remains that way for future generations too.

The first-time experience of hearing "voices from thin air" is unforgettable.

pfannkuchen• 3 years ago

Did you do this before you ever used a full on radio? That seems hard to believe, so I guess you are implying that it is an experience that feels different. I wonder how so?

jgrahamc• 3 years ago

A bit like this: https://blog.jgc.org/2012/02/my-foxhole-radio.html

BoxOfRain• 3 years ago

It's a shame a lot of Europe is either killing off its AM output or already has which will render this impossible, the last transmitters other than a couple of low-power enthusiast stations including the venerable BBC Radio 4 longwave are being shut down over the next couple of years.

Definitely reckon Ofcom should open the band up to hobbyists given it's not much good for anything else.

discretion22• 3 years ago

136KHz is available : https://rsgb.services/public/bandplans/#5

and 472KHz (https://rsgb.services/public/bandplans/6/)

and 1.8-2Mhz (https://rsgb.services/public/bandplans/7/)

There a surprising amount of things it can be used for and some really interesting innovation at the bottom end of the spectrum. Well worth getting qualified as an Amateur operator if you want to experiment.

datpiff• 3 years ago

DRM can be useful. Unfortunately hard to google because of the other DRM. https://en.wikipedia.org/wiki/Digital_Radio_Mondiale

cxr2• 3 years ago

blue razor blade

I first ran across the designs for these radios in a corner of the Old Web on a site called Bizarre Stuff You Can Name In Your Kitchen:

<http://web.archive.org/web/20040918174026/http://www.bizarre...>

cxr2• 3 years ago

Coming back to correct this obvious typo so that site search (and outside crawlers) will pick it up. The correct name is: Bizarre Stuff You Can Make In Your Kitchen.

Pxtl• 3 years ago

I wonder if he had any relation to Amar Bose of the Bose corporation?

Googles

Nope.

29athrowaway• 3 years ago

The other day I learned that the National Ignition Facility uses actual cat whiskers.

https://www.cbsnews.com/news/nuclear-fusion-60-minutes-2023-...

Michael Stadermann: All the components are brought together under the microscope itself. And then the assembler uses electromechanical stages to put the parts where they're supposed to go-- move them together, and then we apply glue using a hair.
Scott Pelley: A hair?
Michael Stadermann: Yeah. Usually something like an eyelash or is similar, or a cat whisker.
Scott Pelley: You apply glue with a cat whisker?
Michael Stadermann: That's right.

timthorn2• 3 years ago

They regained prominence in World War II because of their ability to operate at microwave frequencies

I'd always understood the WWII relationship with cats whiskers to be due to PoWs making radios from materials that they had access to.

Edit: some evidence to suggest my understanding wasn't wrong, if not complete: https://www.bbc.co.uk/ahistoryoftheworld/objects/C5q84AOFTtq...

segfaultbuserr• 3 years ago

They saw two forms of uses during WW2, both low-tech uses and high-tech uses.

Crystal detectors went out of favor soon after vacuum tubes came to prominence, and eventually many researchers almost forgot them entirely due to their outdateness. Later work in microwave electronics made people rediscover their usefulness. Post-war advance in semiconductors made it possible to manufacture small-signal and microwave diodes consistently, finally making them no longer notoriously inconsistent devices. They remain in use for RF/microwave circuit today.

Of course, there was also the work by the Indian physicist Jagadish Chandra Bose, an outlier who used crystal detectors to reach millimeter-wave frequency around 60 GHz already in the year 1900 before everyone else. But as far as I can see, his work had limited influence since it was far ahead of his time.

In Crystal Fire: The Birth of the Information Age, a definite book on semiconductor history, it described the amazement of this rediscovery:

In the mid-1930s [George] Southworth was trying to detect ultrashort radio waves around a tenth of meter long—what he then dubbed “hyper-frequencies” and are today called microwaves—using specially designed vacuum tubes. But he was having little success. Inherent time lags in the flow of electrons through them were simply too great for the tubes to cope with these extremely short, rapidly oscillating waves. Copper oxide rectifiers didn’t work any better, either.
Frustrated, Southworth decided to try one of the old “cat’s whisker” crystal detectors he had used in radio sets during the Great War, when he served in the Army Signal Corps. These quirky devices had fallen gradually out of favor when vacuum tubes became popular during the 1920s. By the mid-1930s it had become almost impossible to buy one in an ordinary radio store.
So Southworth hopped a train bound for lower Manhattan, where he knew of a secondhand radio market on Cortlandt Alley, near Canal Street. Rummag ing around on the dusty back shelves of one tiny shop, he soon found a few old cat’s-whisker detectors. After bargaining with the shopkeeper, he carried them back to Holmdel, where he dusted them off and carefully inserted one into his receiving apparatus. He began searching around on its surface for a suitable hot spot. Finally, after hunting almost an hour, he found a good one.
And it worked! At last, he could detect his ultrashort-wave, hyper-frequency radiation.

alehlopeh• 3 years ago

For every scientific achievement, someone in India discovered it decades before.

adrian_b• 3 years ago

Nope.

Semiconductor diodes were needed for radars, because at such high frequencies the vacuum diodes such as those used in lower frequency radios were inefficient.

Because better radars were a priority during WW2, large amounts of money and work were allocated for developing methods for making better semiconductors.

The most important place where such research was done were the Bell Laboratories. Before WW2, the available semiconductors were very impure and because of that their true properties were hidden.

During WW2 methods to make large quantities of pure germanium and pure silicon have been developed. With the new pure semiconductors, better point-contact semiconductor diodes and better radars were made.

The discovery of the bipolar transistor in December 1947 at the Bell Laboratories was just a normal consequence of their work done during WW2, which left them with a much better knowledge about semiconductor properties and with large amounts of pure semiconductors, on which they could do experiments.

So like the nuclear energy industry is a product of the WW2 research for making nuclear bombs, the semiconductor industry is a product of the WW2 research for making radars.

In both industries, the critical technologies were methods of purification, needed to make enriched uranium and plutonium, and respectively pure germanium and pure silicon.

pests• 3 years ago

I'm current reading "The Making of the Atomic Bomb" by Richard Rhodes.

It's interesting you say that because many scientists they wanted for bomb or nuclear research were sometimes preoccupied with radar. It comes up multiple times in the book.

Is there an equivalent book for the work on radar and all the development that went into semiconductors and transistors for radar during the war?

ggandhi• 3 years ago

They also had memristive properties: https://ieeexplore.ieee.org/document/6518277

1901: Semiconductor rectifiers patented as “cat's whisker” detectors

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