> I'm not sure you can say that Edison (or actually his team) invented the
> radio tube. It was Fleming (of Britain) who added the plate and thus
> made an adjustable gate/valve out of the device. Without the gate it's
> just a light bulb.
Uhm, you've got your facts a bit mixed up, Mark. Edison (actually as you
note, one of his engineers by the name of Charles Batchelor but working
under Edison's directive) did try adding a plate, in an attempt to gain
longer life from his light bulb, and published a note that the plate would
only pass current when it was positive in relation to the filament. This
was even known as the "Edison effect", since it was a great puzzlement to
the scientists of the day. They had actually already observed thermionic
emission (modern name for the Edison effect) while studying the light bulb;
the experiment with the plate was likely triggered by their attempts to
explain the effect. Edison even got a patent on a light bulb with a plate
in it, but he was using it to try to measure voltage or some such.
Fleming was the first to realize that the Edison effect could be used to
detect radio waves, and is credited with the first practical vacuum tube
diode. But all he did was realize how Edison's invention could be utilized,
Edison built and described the diode first.
It takes more than a plate to make a "adjustable gate/valve"; it also
requires a grid between the filament and plate. Lee de Forest (an American)
is credited with being the first to do this. He was also the first to build
a radio transmitter that could send voice, rather than just Morse code.
Randall
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