Radio-frequency amplifiers
نویسنده
چکیده
Electron tube amplifiers may make use of either radio-frequency amplification or audio-frequency amplification, or both. Radio-frequency amplification consists in the amplification of the received radio-frequency current before it is detected. The use of radio-frequency amplification makes it possible to receive a very weak signal which can not be heard at all if only audio-frequency amplification is used. The coil antennas used in direction finding work receive only a very feeble signal, and for satisfactory reception with coil antennas it is necessary to use radio-frequency ampli-
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