Radio Vacuum Tubes
Radio vacuum tubes were crucial to the development of radio, television, telephone, computers, radar and reproducing sound. Without radio vacuum tubes these systems would not have developed on such a wide spectrum nor would they have become so practical and easy to use. Their status today is owed to many events and people, but it is the radio vacuum tube that gave them the ability to initially create the electrical signal they all use. The tube is a compact form that allows the movement of electrons to be controlled and a signal to be created. The ability to plug them in and unplug and replace them when they fail made the use of electronic equipment more convenient.
Components of a Radio Tube
Radio vacuum tubes are created to be insulating and heat resistant. The exterior, usually a tube shape, is made of glass, metal or ceramic. The tube contains electrical conductors (electrodes) that are attached to prongs or leads that extend away from the tube and are used to plug into a tube socket. Visually, the vacuum tube resembles the light bulb---it has a filament that is vacuum sealed in a glass bulb (tube in this case). A metal plate in the bottom of the tube is used to help create the electrical current.
Producing an Electrical Charge
When the radio or equipment is turned on, the filament (the cathode) heats up and releases electrons into the vacuum sealed space. The cloud of electrons is negatively charged. The electrons are drawn to the small plate (the anode) of metal located at the bottom of the tube, which is positively charged. This creates a flow of electrons moving from filament to plate. The attraction of the negative charge to the positively charged plate produces an electric current. This electrical current can pass through the sealed environment of the radio vacuum tube. This is a diode environment or a one-way current. It produces a lot of heat during the course of its use, which eventually contributes to the tubes demise and the need to replace it. Air that leaks into the tube can also cause its eventual need to be replaced.
Modern Electrical Signals
The vacuum tube was long ago replaced by transistors and diodes which are much more efficient, cheap and reliable devices for creating electrical signals. There are still applications and devices, however, that use tubes. High-powered radio transmitters still use them as do audio amplifiers. Variations on the radio tube are used in microwave ovens. Older television sets and computer monitors use cathode ray tubes. These are quickly being replaced with flat panel technology.