The Vacuum Tube as an Amplifier
By B. F. McNamee
Radio for July, 1922
The type of vacuum tube used as an amplifier is the "hard" or high vacuum tube. The vacuum is so nearly perfect that there is no noticeable effect of gas molecules; in fact, for practical purposes it may be considered a perfect vacuum. The "soft" tube, that is one containing a certain small pressure of gas and intended for use as a detector, can be used to a certain extent for amplification purposes. However this almost always results in distortion which would prohibit its use as an amplifier in radio telephone work, and its use is also restricted because it will not work with high plate voltage, thus limiting the strength of signals that can be obtained.
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