Newnes Radio and RF Engineering Pocket Book, 3rd Edition

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channel spacing equipment). It may be quoted with reference to a

pre-emphasis curve.

• Switching bandwidth. This is the frequency range over which the

transmitter will operate without retuning and without degradation of

performance. Much equipment is now specified to cover a complete

frequency band, e.g. 146–174 MHz, without retuning.

10.2 Receivers

10.2.1 Receiver functions

A receiver’s functions are:

• Detect a weak signal; the minimum level, which may be as low as

0.25 microvolts, defines the receiver sensitivity.

• Amplify a received signal and maintain the information contained

in a minimum strength signal at a minimum of 12 dB above the

electrical noise level (signal-to-noise ratio). If the audio distortion

produced in the receiver is also taken ...