The stages of a TSF

fig.1 Eurelec radio

Introduction

The structure of radio receivers has evolved over time. The first ones only processed telegraph signals, then amplitude modulation (AM) radio. Reception in frequency modulation (FM) allowed listening without interference and in a more complete audible frequency spectrum for the human ear. Stereophonic broadcast reception finally allows us to speak of High-fidelity.

Receivers can be classified into the following categories:

• Crystal radios
• Regenerative receivers
• Superheterodyne receivers
• FM receivers (stereophonic or not)
• Digital receivers (not covered here)

The crystal radio.

It allowed receiving amplitude modulation broadcasts without any energy input from a battery or mains power supply. The energy vibrating the earpiece diaphragms comes from the carrier electromagnetic wave. A very good antenna was needed and being close enough to the transmitter to have audible sound. A description of this type of receiver is available on the page a crystal radio of this site.

The frequency change receiver, known as superheterodyne

fig.2 structure of a vintage radio

Here, the block diagram and schematic of a superheterodyne radio. It appeared in the 1930s. Current analog radios are still based on this principle.

The table below lists the building blocks of a vintage radio according to its typology