Ye Olde "Cat's Whisker" Diode construction ?? - Page 1
Forum section: electronics / general

author: GlennSprigg
author_rank: Super Contributor
timestamp: June 15, 2019, 10:34:39 am
content: As part of one of my simplistic 'Steam-Punk' radio projects, I want to keep it as genuinely old, as possible.Instead of using a typical 'newly made' diode, (like the 1N34A Germanium Contact Diode), I want to make it!!I've reviewed many sites, (includinghttps://en.wikipedia.org/wiki/Crystal_detector), and I know about thevarious types of 'crystal', peculiarities, pressures, spot-location issues, reliabilities & failure-rates....So I'm wondering if others have ever made one, and how successful you were !!I understand, & have the mech/tech abilities, but should I leave it in the 'Too-Hard/Fiddly' basketIf so, then maybe I'll build a 'fake' (steam-punk style) realistic looking unit, with a 1N34A inside it !!

author: exe
author_rank: Unknown
timestamp: June 15, 2019, 11:51:57 am
content: Check on youtube, there are a few semi-successful attempts to build semiconductor devices at home. Although those I saw were silicon devices, not germanium... You may need a silicon wafer and some chemistry.

author: GlennSprigg
author_rank: Super Contributor
timestamp: June 15, 2019, 12:16:00 pm
content: Thanks, but I only mentioned 'Germanium' as used in 'modern' diodes.I will look at 'Silicon' though....

author: ciccio
author_rank: Frequent Contributor
timestamp: June 15, 2019, 01:06:01 pm
content: I built my first radio receiver (decades ago) with a Galena chrystal detectorWikipwdia:https://en.wikipedia.org/wiki/GalenaIt worked (I was 6 and my family did not believe it).Best regards

author: ptricks
author_rank: Frequent Contributor
timestamp: June 15, 2019, 01:23:56 pm
content: Did it with an old school HAM radio guy , actually what got me started in electronics.We used a safety pin, razor blade, coffee can, copper wire, paper tube from paper towels, crystal earphone.wrap the wire copper wire on the paper tube, sand off a strip of enamel on the wire across the coil of wire to make your tuning coil.Cut the metal coffee can into a strip and place the strip so it contacts the top of the coil and attach other end to a board with a screw so that the loose end slides across the coil, this is the tuner.razor blade, needs to be the blue steel kind or one that is heated with a torch till the metal changes color.Safety pin , needle end is put touching the razor blade just barely,otherwise known as a foxhole radiohttps://cactusbush.wordpress.com/tag/foxhole-radio/

author: Cyberdragon
author_rank: Super Contributor
timestamp: June 15, 2019, 02:13:34 pm
content: Do not use refined semiconductors. Crystal detectors are always made using natural minerals.It is not that hard, but a stable (IE movable) detector all depends on mechanical stability of keeping the spring (whisker)exactlywhere it is plated at a constant pressure. This usually involves some sort of setscrews, or friction. There are many different crystals that will work, and whisker type (different tensions) matters too depending on the crystal type. The best one for newbies would be galena and a relatively loose whisker. Though as a kid I built a crystal set using tuner parts from an 10-in-1 transistor experiment kit and peacock ore with a random spring (chosen for tension) for a whisker mounted to a wooden toy dinosaur head as the detector. It worked well enough to drive a small LM386 amp directly when the signal was heterodyned with a battery operated sig gen. Used it to play Christmas carols from the local AM station on Christmas day.Note: to test detectors outside of a receiving circuit, place them in series with a sig gen and scope to check for rectification. (do not pass too much current)Side note: Carborundum/silicon carbide forms natural LEDs on it's surface.

author: free_electron
author_rank: Super Contributor
timestamp: June 15, 2019, 02:27:02 pm
content: Quote from: ciccio on June 15, 2019, 01:06:01 pmthis.go to a store that sels minerals, get a piece of galena (costs a few dollars ) , and a rusty needle.done.

author: Ian.M
author_rank: Super Contributor
timestamp: June 15, 2019, 02:29:49 pm
content: Back in the day (pre WWII), radio parts suppliers sold specially selected (for activity) Galena crystals. Unfortunately mineralogical specimens on Ebay etc. tend to be chosen for their visual appeal which makes them poor detector crystals.There's an interesting article on radio detector grade 'steel' Galena here:https://lessmiths.com/crystal/sgalena.shtml

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: June 15, 2019, 04:01:28 pm
content: http://sparkbangbuzz.com/zinc-oxide-diode/zinc-oxide-diode.htm

author: GlennSprigg
author_rank: Super Contributor
timestamp: June 17, 2019, 09:53:06 am
content: Quote from: free_electron on June 15, 2019, 02:27:02 pmYea... I get that bit !!, but was curious about peoples practical successes/failures !(It's ok... I know you were only making light of it)Thanks to all... I'll get on with making it now, so it looks 'chunky' & artistic, (along with the other parts)so it will look as though it would 'fit in' on Captain Nemo's Nautilus, resplendent in polished Copper !

author: GlennSprigg
author_rank: Super Contributor
timestamp: June 17, 2019, 10:06:16 am
content: P.S. Oh, and I forgot !!!As an aside, in relation to old arguments about Electron/conventional current-flow...It was reported that the original ARROW head for a Diode, was designating a 'Cat's-Whisker'against a crystal-face. Not to depict Conventional Current !!!!

author: floobydust
author_rank: Super Contributor
timestamp: June 17, 2019, 08:15:08 pm
content: I remember stories of crystal radio guys trying a third electrode on the galena crystal, with some getting amplificationI think these guys really discovered the transistor?Shockley and Bell Labs then just figured out the physics and came up with something repeatable.

author: Cyberdragon
author_rank: Super Contributor
timestamp: June 17, 2019, 10:37:34 pm
content: Quote from: GlennSprigg on June 17, 2019, 10:06:16 amActually, the early crystal detector symbol featured a much smaller arrow and a fatter line.Quote from: floobydust on June 17, 2019, 08:15:08 pmYes and no. The third electrode on galena appears to be a myth, but weak crystal amplification and oscillation was discovered early on. However, without understanding of semiconductor physics, they were hard to replicate. A few prototype radios were built this way, but I'm not sure how well they worked.https://earlyradiohistory.us/1924cry.htmhttps://earlyradiohistory.us/1924sens.htm

author: floobydust
author_rank: Super Contributor
timestamp: June 18, 2019, 08:22:30 pm
content: Let me know where it was found to be a myth, as I believe it's the real place the transistor was discovered. The old crystals surely had impurities and other elements present.

author: Cyberdragon
author_rank: Super Contributor
timestamp: June 18, 2019, 11:19:47 pm
content: Quote from: floobydust on June 18, 2019, 08:22:30 pmThere is no evidence or mention I can find on transistor effects discovered in galena. FET patents go back as early as 1925 and 1934, however no such device was ever constructed back then. Transistor research came from research into high speed germanium diodes.

author: rfeecs
author_rank: Frequent Contributor
timestamp: June 18, 2019, 11:57:56 pm
content: How the point contact transistor came about is very well documented. For example Bardeen's Nobel lecture "Semiconductor research leading to the point contact transistor" pretty much tells the whole story:https://pdfs.semanticscholar.org/d607/5e30df3c49fb735bb1dece3d857e8f60825e.pdfThey were trying to make a Field Effect Transistor, and studying the problem of surface states, when they discovered the transistor effect.It seems like such a simple device, and so similar to a point contact diode. It does make you wonder why nobody found it earlier.The theory they give on how it works seems to rely on an N type semiconductor with a special surface treatment that inverted the surface, creating a P-type layer.One breakthough was using Germanium, which worked much better than Silicon.It seems unlikely that an experimenter could come up with this combination by chance. But I guess you never know.

author: Brumby
author_rank: Unknown
timestamp: June 19, 2019, 03:03:53 am
content: EVERYBODY was an experimenter in the early days. Some were just better funded.

author: floobydust
author_rank: Super Contributor
timestamp: June 19, 2019, 05:15:02 am
content: Quote from: rfeecs on June 18, 2019, 11:57:56 pmThat lecture seems to be rubbish, overlooking the beginnings?In 1874 galena (lead sulfide) point-contact rectification was discovered.The1901 Milestonefiling of US patent for the crystal detector.The silicon point-contact diode was patented in 1906 by US engineerGreenleaf Pickard.He tried thousands of minerals and found 250 that worked. Silicon carbide patent was filed two weeks after.Julius Lilienfeld 1926 patent for field effect three-electrode structure using copper-sulfide semiconductor."Legal papers from the Bell Labs patent show that William Shockley and a co-worker at Bell Labs, Gerald Pearson, had built operational versions from Lilienfeld's patents..."

author: JohnPen
author_rank: Regular Contributor
timestamp: June 19, 2019, 08:50:54 am
content: As a ten year old in the the 1950s I acquired a small germanium crystal. I mounted it between 2 angled drawing pins on a piece of wood and wound a coil for medium wave frequencies. Added a tuning capacitor and a pair of headphones with a capacitor in parallel and managed to pick up a few radio stations. I had a 30 ft long wire in my parents roof space. The strange thing was a I picked up a morse code transmission as well which must have been a modulated because it was a pure tone not a thump. I am sure that many an amateur experimenter has discovered all sorts of strange physics effects which eventually someone else develops into a feasible product. I wonder what will be next?

author: GlennSprigg
author_rank: Super Contributor
timestamp: June 19, 2019, 10:26:32 am
content: I 'sort-of' was finished here, but then I got to 'wonderin' !!!(Loved all the replies by the way....)This Crystal 'Detector' is/was really nothing more than a 1/2 wave rectifier, to chop off onehalf of the amplitude-modulated 'carrier' wave. So would it not result in a 'better' signal, to usean equivalent 'full' wave rectifier, to fill in the gaps !!!

author: Ian.M
author_rank: Super Contributor
timestamp: June 19, 2019, 11:07:18 am
content: Yes, but that would require four reasonably well matched cats whisker detectors, and an isolated coupling winding to drive them. Keeping stray capacitances to ground balanced would be challenging and keeping four cats whisker detectors in adjustment would be a royal PITA. Also a x2 increase in signal power is only 3dB so its a barely perceptible improvement to the human ear. Its generally much less hassle to double the size (or rather the effective energy collecting area) of the antenna, and unless its either very large to start with or you are constrained by available land area or support structure positioning, or already have a near optimal dipole antennae for the wavelength in question, probably comparable in cost.

author: floobydust
author_rank: Super Contributor
timestamp: June 19, 2019, 10:16:41 pm
content: Of the other radio detectors at the time,The Fleming valve-diode was on the 1912 Titanic radio, state of the art and used a pair but also had amagnetic detectoror "Maggie", I believe. It might be full wave, but is a bizarre way to detect RF. Nobody probably understood it.The MarconiCohererhad the worst sensitivity.The crystal detector purity of the minerals was the main issue, and I think everybody tried everything on crystal detectors. But too sensitive to vibration and oxides. It seemed to break up the monopoly of the Fleming valve-diode technology that Marconi had. That "third electrode" also was added to it to make a triode.

author: rfeecs
author_rank: Frequent Contributor
timestamp: June 20, 2019, 09:49:17 pm
content: Quote from: floobydust on June 19, 2019, 05:15:02 amThis old newgroup thread may be of interest:https://www.electronicspoint.com/forums/threads/the-lilienfeld-transistor-and-evidence-of-a-bell-labs-coverup.69008/Various posts in the thread claim, among other things, that:Bell Labs covered up Lilienfeld's invention of the transistor;Lilienfeld actually built a radio based on his transistors;Other people have built working versions of Lilienfeld's transistors;People even before Lilienfeld were experimenting with devices with multiple point contacts and different biasing schemes;There is a research paper describing experiments with Galena based point contact transistors:Crystal Triode Action in Lead Sulphide,P. C. Banbury, H.A. Gebbie, C. A. HogarthProc. Conf. Semi-conducting Materials pp78-86.H.K. Henisch (ed), Butterworth's sci pub LTD 1951

author: Cyberdragon
author_rank: Super Contributor
timestamp: June 21, 2019, 12:43:54 am
content: I see where the myth came from now. But that thread seems to be nothing but a standard conspiracy theory about corperate big wigs stomping on scientific progress and some remarkable breakthrough. No, I highly doubt they had full transistor radios in the 30s, they simply did not fully understand the principles well enough to reliably replicate them. If you look at the patents meantioned, as the thread states, they didn't even know about the quantum physics of the transistor, they tried to explain the charge flow like some sort of fluid. It wasn't untill Bell discovered the actual physics were they able to reliably replicate the device.

author: floobydust
author_rank: Super Contributor
timestamp: June 21, 2019, 06:06:43 am
content: In that old thread, one post:"Has anyone mentioned that around that time, both before, during and after Lilienfeld, that some radio amateurs, not being rich enough to afford a tube, fiddled with point contactS (yes, plural) on crystals? Various configurations were used, including pressure on one or more of the contacts, as well as various *biasing* schemes. And there were claims of gain . . but . . reproducibility was sadly lacking. Adding true and verified stories with dates would enrich the history!"I didn't see any evidence.Bell Labs was able to make a commercially viable device, using prior art. But did they invent the (self-named) transistor?Nobody really understood conduction mechanisms through solids, models of the atom were not great, high-purity minerals hard to find.

author: ivaylo
author_rank: Frequent Contributor
timestamp: June 21, 2019, 06:38:15 am
content: I’ve made synthetic galena as a teenager following a recipe in an old amateur radio book (led from old car battery, sulphur from the pharmacy). Worked fine, but we also had a powerful MW transmitter not far from us. Not finding much online now, these people are talking about it though -http://theradioboard.com/rb/viewtopic.php?t=3606&start=15

author: GlennSprigg
author_rank: Super Contributor
timestamp: June 26, 2019, 09:14:06 am
content: Back on Page-1, a bunch of various comments, beginning with/after floobydust on June-18, werediscussing the 1st 3 electrode 'Transistor', and reports of doubts(?) about who 'invented' what,between Bell, Japan & RCA. Here is a very interesting (40-min) documentary that covers all the facts(?)

author: rfeecs
author_rank: Frequent Contributor
timestamp: June 26, 2019, 05:36:13 pm
content: This is a pretty entertaining one,"Transistorized" from PBS.It is mostly from the Bell Labs perspective: