1N34A Datasheet, 1N34A Germanium Diode Datasheet, buy 1N34A Diode. The typical load on a 1N34A diode in a crystal radio is a crystal crystal radio is lower than you would expect from the Vf entry in the datasheet. 1N34A Germanium Diode, Package: DO Can be used in many AM, FM and TV-IF applications, replacing point contact devices.. Applications. TV audio.
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I heard no sound from it through a piezo buzzer pressed against my ear and figured it was maybe because of the diode, so I looked around for the datasheet for the 1N34A to read its characteristics. It lists Vf as 1V at 5mA. It is my understanding that Ge diodes were the choice for crystal sets because their low Vf does not load the tuned circuit. Perhaps I am misunderstanding the datasheet? The trick lies in the combination. With a lower If, Vf is also lower.
Since a crystal earphone draws very little current, Vf is also lower. As you can see from this diagram from here. The 1N34A will conduct 0. You need the crystal earphone to avoid loading the tuning circuit and to keep dxtasheet Vf low enough for the diode to demodulate the signal. In reponse to comment: It may well be the diode that is causing problems.
The 1N is made for lower frequencies and higher currents datasheet a signal diode. Here’s link to a site about crystal radios with some hints about schottky diodes: According to that site, you will need a bias current for most schottky diodes to get good performance. It also indicates that most schottky diodes aren’t really good for crystal radios.
From my own experience in building crystal radios, you would be well advised to build the first one using exactly the parts recommended and exactly the schematic of someone who has built one successfully.
Germanium Diode 1N34A
They are finicky enough that even slight variations will cause a dataeheet – substituting parts is just asking for trouble. Another thing to keep in mind is that they don’t have fanstatic range. My biggest problem when building one as a kid was that we lived so far away from any transmitter that you pretty much had to get everything perfect and have a good antenna in order to pickup anything at all.
Being a datasheeet, of course, meant that I never got things really good enough. Use a proper crystal radio earphone! A piezo buzzer is meant to BUZZ at a particular frequency.
How well it will do anything else is anybody’s guess. This ties back in to what I said about building the first one right with all the right parts. Once you have a working receiver, you can try using the piezo buzzer and see what it does and how it changes things – but that is an experiment for AFTER you have a working receiver.
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MichaelK 4 Also worth noting is that Vf is dependent on temperature. Interesting you mention temperature.
I guess it didn’t help that I tested this radio outside in -5 degrees Celsius. I tested it indoors as well though and it still didn’t work datasehet it wasn’t exclusively the temperature. The answer lies in a combination of things. The typical load on a 1N34A diode in a crystal radio is a crystal earpiece with an impedance of 20kOhm.
The 1N34A conducts much smaller currents with a lower Vf.
As you can see from this diagram from here, The 1N34A will conduct 0. You need a low Vf because of the modulation scheme, not to avoid loading the tuning circuit. Thank you for your answer and the clarification about why I need a low Vf and crystal earpiece.
But at mA it looks like it conducts 0. Would this still be a suitable replacement for a Ge diode? It is completely possible that another part of my circuit is to blame, I just want to rule out the diode. I think that “a piezo buzzer” today isn’t comparable to a crystal earpiece. Try locating an actual crystal earpiece and give it a go. How did I miss that?
Isn’t a crystal earpiece just a piezo buzzer? If not, I hath been lead astray by this link and videos. Thanks again for your replies. They both use a piece of piezoelectric crystal to work. A buzzer is made to work specifically at a particular frequency.
Whether and how well it works at other audio frequencies is anybody’s guess. It may work well, it may not. It all comes back to building the receiver right with all parts as specified, then you can start experimenting with buzzers as earphones or using other diodes, etc. Get it working right, first, though. It lists Vf as 1V at 5mA It’s never this black or white: Andy aka k 10 Sign up or log in Sign up using Google. Sign up using Facebook.