Crystal Radio Fake 1N34A Diodes! Easy Test (4K)
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- Опубликовано: 5 июл 2024
- Sadly there are lots and lots of online sellers selling fake 1n34a diodes. Most likely they are Schottky diodes that will give lower performance and distorts the analog radio signal into something square-ish.
Let's do an easy test that does NOT require a frequency generator, oscilloscope or other high dollar test equipment. Only a decent VOA meter and a 1.5 volt battery is required.
This is one of the videos I referenced. The guy shows the difference in waves of the 1n34a and schottky. • 1N34A or NOT 1N34A ???
UPDATE: I bought some D9K diodes that are good substitutes for the 1N34A on ebay from "Stavr-Tube&Tones up grade".
Crystal Radio--A Good 1N34A Diode Substitute • Crystal Radio--A Good ...
Video: Best/Easiest DIY Crystal Radio - No Batteries, No External Power (4K)
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Crystal Radio videos that might be interesting.
Crystal Radio--A Good 1N34A Diode Substitute ruclips.net/video/phD_2Wm79gs/видео.html
How To Make A Crystal Radio (basic): Best/Easiest DIY Crystal Radio - No Batteries, No External Power (4K)
ruclips.net/video/fLVCqZGpv3U/видео.html
My Crystal Radio Does NOT Work (FIXES for common problems): ruclips.net/video/kCxQ8iPQx4s/видео.html
Advanced Crystal Radio: ruclips.net/video/mh5KxCpbQ5U/видео.html
UPDATE: I bought some D9K diodes that are good substitutes for the 1N34A on ebay from "Stavr-Tube&Tones up grade".
This is one of the videos I referenced. The guy shows the difference in waves of the 1n34a and schottky. ruclips.net/video/jfCh87JP92I/видео.html
D9 family - USSR made Germanium diodes. D18 is much better.
In the close up of the genuine 1N34A you can see the "cat's whisker" making the point contact. :)
You have come up with a good way to test for germanium diodes, the only thing I would do different is put a redidtor in series with the battery to limit the current. That way if the diode is shorted or labeled backwards the fuse in the meter dosn't blow.
A good idea.
1N34/34A when excited by a sine wave does not pass a sine wave (unless biased so as to be always conducting) due to the wave reverse biasing the diode for half of the wave. This is one of the principles of AM detection. Niggling point, perhaps, but those curious enough to go look on an oscilloscope will see that.
I was not aware of the reverse leakage current test. Thank you for pointing that out. This is something new to research to expand my knowledge.
As the description points out, Schottkys (as well as silicone) diodes will work in a crystal radio but give vastly inferior results compared to germanium types.
Thanks for the info. I will test mine.
I had purchased some fake 1N34A diodes which exhibited no measurable reverse leakage current. I`m pretty sure they are Schottkeys. So I hunted through my ancient junk box and found a germanium NPN transistor. The base - emitter junction worked just fine in a crystal radio.
Interesting. I will have to try that.
Speaking as a BSEE who studied semiconductors: not even all Schottky diodes are created equal. Some feature a higher forward voltage, some a lower -- even lower than germanium's characteristic 0.3 volts in some cases. Lower forward voltage is better in detecting low voltage signals. Assuming the data sheet and supplier are honest, if one had to use Schottky this characteristic is a way to identify better suited ones for this purpose. I agree it is such a shame that the cheap-junk trend of the West has moved any remaining germanium semiconductor production to China, where honesty is dubious since nobody with, say, a brand name at stake is controlling quality on that end.
Before the Internet they build good stuff
Wow, counterfeit diodes?! Never thought I'd see the day lol
Me too. I knew that the ones I bought recently did not work very well, now I know how to weed out the real from the "substitutes."
Germanium diodes are sensitive to heat. Hold the diode between your index finger and your thumb for 20 seconds; the forward voltage should rise. If it doesn't, it is a fake.
Interesting. I will have to try that, assuming I can keep my fingers out of the circuit!
@@tsbrowniehow’s the outcome?
It sounds like 1n34as are becoming unobtainable.
It might be better to figure out how to make the shottky work.
Would putting a high value resistor in parallel with it make it act mote like a 1n34a?
I have a video on the D9K, which is still easier to get. Also I have videos on using a cat whisker detector with iron pyrite / galena.
Cheers 😁👍
Ich habe es heute mit einem billigen Sanwa Analog Multimeter probiert im Ohm x 100K Bereich 1n60 Dioden die ich vor einem Jahr bestellt habe in Sperrichtung zu messen. Ja und es hat mir mit 3V Spannung ca. 0,5
"Today I tried using a cheap Sanwa analog multimeter to measure 1n60 diodes that I ordered a year ago in the ohm x 100K range in the reverse direction. Yes and it gave me about 0.5 voltage with 3V"
If one wants to go really old school for crystal radios, one can try to get or make a cat whisker galena detector. For something that has to be wired permanently in circuit and not needing adjustment, this is obviously not suitable. A circuit arrangement that boosts the RF voltage (like a step up transformer) may make it more feasible to use a silicon detector with its higher forward voltage.
Got videos on how to make and use them also!
Can't we use one of the junctions on an old germanium transistor?
I have heard that but not tried it. I have my doubts. I have tried all the diodes in my collection going back 50 years and nothing so far comes close to the 1n34a or d9k. Can't see that a transistor junction would be good, but I am open to it.
@@tsbrownie Just tried it. It _does_ work, but a proper diode would probably be better.
The D9k for my experience is not a good diode, because the signal is very low and so , they aren't good for Crystal Set and for DC from RF by Avramenko fork! perhaps that you are more lucky than me but I have seen your note about the D9K see you and please excuse me for my bad English
I have NOT recommended the d9k.
But you have writed that the D9k is a valid substitute of 1n34A
Does anyone have suggestions on where to buy real 1N34A?
Digikey, Jameco, and similar big electronic parts shop should have the real deal. I did a quick search on "where to buy 1n34a diode" and found dozens and dozens of people reselling fakes/bad substitutes they call 1n34a, some at rediculous prices.
I'm also working on a cat whisker detector for crystal radio purists, for when only galena, iron pyrite and such will do.
@@tsbrownie Digikey, at least the Canadian version, does not carry 1N34A. In fact, I have hard time finding any reputable distributor selling 1N34A. That's probably why there are so many fakes being sold out there.
@@pilobondI have been using the D9K lately and it seems to work OK. It was made in Eastern Europe. It does have some oddities, like it seems to quit working properly temporarily if you reverse the diode direction. Maybe it needs to re-polarize or some such. And it's just my opinion, but seems to be a bit (maybe 10-20%) less sensitive.
Schottky = silicon
"the common silicon diode is build with a semiconductor p-n junction, the Schottky diode is build with a metal-n (metal-semiconductor) junction, where the movement of charges through the junction is quite faster than in the p-n junction."
Hello! It is better to use syncronous detector for the crystal radio - I used BF998 MOSFET with shorted gates. There wasn`t any power supply or a battery.
I will have to try that.
@@tsbrownie the important thing - DC current should not flows tgrough earphones.Use electrolytic capacitor between phones and mosfet.And RF blocking capacitor 10nF between drain and ground