MK484 Radio Breadboard Layout

The MK484 radio is extremely simple to construct on a breadboard. The best way to build this is stage-by-stage. The first task is to connect the ferrite coil antenna to the tuning capacitor. You need to keep the wires short, and in this build, I am soldering the ferrite coil wires directly to the terminals of the variable capacitor.

We start by installing the MK484 and the components around it. If you have a crystal earpiece, then you should be able to hear the output from the first 1 µF electrolytic capacitor, which provides the inter-stage decoupling by blocking the DC part of the signal and allowing the AC through.

Then install the BC549C transistor and the biasing components around it. The output of this stage is through another 1 µF electrolytic capacitor. At this point, you should be able to hear the signal through your crystal earpiece. The final stage has the MPSA13 Darlington transistor, and in this stage, we use a 10 kΩ potentiometer to provide simple attenuation of the signal.

In the diagram, the coils L1 and L2 represent the coils within the LT700 transformer. This audio output transformer has three terminals on one side and two on the other. The side with the two terminals connects to a loudspeaker, which should be around 8.0 Ω or 4.0 Ω.

The side where there are three terminals, we do not use the middle terminal, and only use the two outer ones. This is the side of the coil, which the Darlington transistor drives.

The circuit requires power from a PP3 9 V battery, and its wires connect to their respective rails on the breadboard.

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