Vacuum Tube Audion Work

Vacuum Tube Audion Work

This basic device, the diode tube with a grid, is called an "audion." The grid, attached sometimes to an antenna, picks up the high frequency waves emitted by a radio transmitter. In wireless telegraphy, the transmitted impulses are all of the same volume that is, a steady tone of one pitch is sent out. A detector that will pick up this tone at all, even if faint, will serve for wireless communication in a code of dots and dashes. But for voice transmission, the waves transmitted continually vary in volume, corresponding to the rise and fall and the separate sounds of the voice.

A more sensitive detector is needed. The grid serves this purpose. Very weak electrical waves, and very slight variations of volume, have a powerful effect on a steady current that is passed through the vacuum tube. This current is used to operate the diaphragm that reproduces the voice in the radio receiver.