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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Germanium Diode 1N34A
The trick lies in the combination. A buzzer is made to work specifically at a particular frequency. If not, I hath been lead astray by this link and videos. It is completely possible that another part of my circuit is to blame, I just want to rule out the diode. It may work well, it may not. You need the crystal earphone to avoid loading the tuning circuit and to keep the Vf low enough for the diode to demodulate the signal.
With a lower If, Vf is also lower. But at mA it looks like it conducts 0. 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.
Here’s link to a site about crystal radios with some hints about schottky diodes: They both use a piece of piezoelectric crystal to work. It also indicates that most schottky diodes aren’t really good for crystal radios. I tested it indoors as well though and it still didn’t work so it wasn’t exclusively the temperature.
1N34A – 1N34A Germanium Diode Datasheet
How did I miss that? The typical load on a 1N34A diode in a crystal radio is a crystal earpiece with an impedance of 20kOhm.
The 1N34A will conduct 0. Get it working right, first, though. From my own experience in building crystal radios, you would be well advised to build dafasheet first one using exactly the parts recommended and exactly the schematic of someone who has built one successfully.
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. 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.
The 1N34A conducts much smaller currents with a lower Vf. The answer lies in a combination of things.
Germanium Diode 1N34A
This ties back in to what I said about building the first one right with all the right parts. As you can see from this diagram from here.
Isn’t a crystal earpiece just a piezo buzzer? You need a low Vf because of the modulation scheme, not to avoid loading the tuning circuit. Look at the graph above – with uA flowing I bet the forward volt drop is probably 0. Whether and how well it works at other audio frequencies is anybody’s guess.
Andy aka k 10 Interesting you mention temperature. 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. In reponse to comment: Also worth noting is that Vf is dependent on temperature.
MichaelK 4 Sign up or log in Sign up using Google. It is my understanding that Ge diodes were the choice for crystal sets because their low Vf does not load the tuned circuit.