Crystal Radio Antenna Preamplifier

Posted on Feb 5, 2014

Adapting one of my failed Tesla coils into a crystal radio set to show the neighborhood kids. I`ve run into the #1 problem everyone faces not enough antenna to generate a strong signal. I read somewhere that a proper  AM antenna should be between 100 500 ft for good reception (technically known as quarter wavelength). I don`t think anyone living in a city can install an antenna of that size.

Crystal Radio Antenna Preamplifier
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So I managed to push about 60 ² of wire into the air, and I was getting OK results from it but thinking that maybe a simple pre-amplifier circuit would be a good thing to squeeze a bit more performance. So I found this schematic from the Antique Radio Forums. This was designed for a 10 ² antenna and does work quite well. I`m thinking about adding an extra stage of amplification through another transistor does anyone know if this is a good or bad thing Obviously I will be amplifying the noise too, so maybe an audio amplifier would be better, installed after the tuning coil. UPDATE : Since posting yesterday, this article has generated quite a bit conversation behind the scenes one thing that has come up is that replacing the transistor with a 2N5179 and then adding a class B complementary emitter follower on the output would be a good strategy. I`ll be working on this and posting a follow up to show what happens. I am very impressed you took a simple transistor such as the 2N3904 and made a RF amplifer. I have been using the other transistor called the MPF102 to make a preamplifer, but this one you made does not require a fixed choke like the other circuit I have built to improve AM reception. I cannot wait to try this one out for to improve AM and long wave reception. Thanks!

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