9 V AM Radio Circuit

This 2-transistor 9 V AM radio circuit uses cheap and commonly available BC549 transistors. An advantage of this circuit is the use of a single 9 V battery, which can last a very long time and take little space. This circuit is much simpler with fewer biasing resistors and fixed capacitors. The 100 nF capacitor increases the input impedance in order to reduce the loading on the ferrite coil. The 1 µF capacitor is simply for inter-stage decoupling purposes. This is an alternative circuit that I discovered when experimenting and found that it works very well. As usual, we have the first stage transistor performing the RF demodulation and amplification, whilst the second stage performs the AF amplification. Notice that in this circuit design, it is just simple amplification we are aiming for, and we are not employing any regenerative techniques.

If you are new to building simple transistor radios, then the best place to start is by getting an electronics lab. These usually contain many experiments beginning with a simple crystal radio, and then extending into multi-transistor radios, including circuits that drive loudspeakers. An advantage here is that you will not be overwhelmed with having to build your own coil, nor search for specialized components such as a germanium diode or crystal earpiece.

The Ferrite Coil

The ferrite coil in this project is the same one used for the Spy Crystal Radio - Budget Cuts project. If you have already built a crystal radio and have a good coil and variable capacitor combination, then it is better to use that, otherwise you can always use the one shown in the crystal radio article link.

Other 2-Transistor AM Radio Circuits