With nothing more complex than a germanium point-contact diode and an oscilloscope, you can quickly, easily, and cheaply resolve microwave signals, as we are shown with a 2.4GHz wireless mouse.

TRAPATT and BARRITT diodes, microwave bipolar junction transistors (BJT) and field effect transistors (FET), small signal amplifier design, new devices like HEMT and Si-Ge devices, traveling wave ...

A humming noise from a microwave as a sign of a worn-out diode, which controls the flow of electricity in one direction and restricts it in the other, which stops the microwave from generating heat.