THE LITTLE GLOWING MARVEL

A statement was made on the history channel that the vacuum tube had to be invented before the radio could be invented. The logic behind the statement was that oscillators could not be made before amplifiers. It is true that oscillators could not be built before amplifiers but radio communications predates the use of these little glowing marvels as amplifiers by 20 years. All that was needed was a spark gap transmitter and a coherer detector for a receiver and radio came into existence. Later the Peroxid of Lead detector came into being followed many others including the Electrolytic Detector, the Barretter, Carborundum Detector, the Silicon Detector, the Perikon Detector, and the Galena Detector, the last three could be lumped together and called a crystal detector. All of these preceded the use of the vacuum tube as an amplifier.

Though they precede the use of the tube as an amplifier they technically don’t precede the vacuum tube. The summer of 1895 is considered the beginning of radio communications when Guglielmo Marconi was able to transmit and receive a signal over approximately 1.5 kilometers (approx. 1 mile). The vacuum tube history began in 1883 when Thomas Edison, while trying to improve the incandescent light, discovered that if he placed a small metal plate in the glass envelope of the light and attached the metal plate to a positive charge while the negative charge was on the filament electric current would flow across the vacuum inside the envelope. This came to be known as the Edison Effect but Edison did nothing more with it.

In 1904 Sir John Fleming found he could use the Edison Effect to detect radio signals. So over the 9 years between Marconi’s invention and Fleming’s discovery the vacuum had no connection to radio. It was not until 1915 when Lee DeForest placed a grid inside the diode between the filament and the plate that amplification was possible. With the invention of the Audion, the first name for the vacuum tube, true continuous wave propagation became possible. The Audion later became known as the Fleming Valve which it is still called in many countries but in the United States of America it is called a vacuum tube.

Not only did it provide the necessary essential to make oscillators and detectors but amplifiers and mixers which allowed the superhetrodyne radio.

It was these little glowing marvels that bridged the road between the wide band, short range, loud smelly spark, and insensitive passive detectors and the present solid state DX in a box radios.


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