Analyzing and troubleshooting a modern AM/FM radio, digital radio, or TV can be a pretty daunting task. However, a common AM radio is easy to understand, experiment with, and repair. Learning about that will help you understand more complex circuits later. That’s the idea behind the Elenco AM radio which is built on a wide-open PCB with markings for all the important sections. [The Offset Volt] uses one of these to explain how a receiver works, especially how a diode detects the signal and how the automatic gain control works.
Between a series of diagrams and live scope demonstrations, you can see the effects of capacitance in the receiver along with other circuit effects.
There are only a few simple constructs needed to understand a large number of circuits. Voltage division, resistor/capacitor charging, and capacitive/inductive resonance will cover a lot of ground. You’ll see that in several places here — many manifestations of just a few concepts.
Even if you cut your teeth on old AM radios, this kit might be just the thing to get a young person started learning the mysteries of radio. How simple can a radio be? Pretty simple. If FM is more your speed, you might enjoy reading about its history.