A popular noise limiter in CB units is the so-called series-gate circuit, an old standby but which nevertheless does a most effective job. One minor difference in various sets in whether or not you can switch the noise limiter in and out of the receiver circuit, or whether it is always functioning. Don’t reject a set if you can’t switch on the noise limiter; it’s probably an automatic type that adjusts itself according to signal conditions.
One innovation on the CB scene is the noise silencer circuit, which is an advanced and sophisticated type of noise limiter. Its specialty is crushing impulse type noises, such as are created by motors. Since it isn’t completely effective on continuous-type noise, it is usually supplemented by a second limiter. A switch allows you select standard noise limiting or a noise silencer.
Sensitivity is the ability of the CB rig to pick up weak stations. Since the sensitivity circuits are the first things which the incoming signal encounters in your rig, they are commonly known as the front end.
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Better-made (and usually high priced) gear has a stage or two of radio-frequency (RF) amplification on the front end to give incoming signals a little more ZIP! The current rage is for Nuvistors to perform this task. Nuvistors are tiny metal tubes which give high amplification with little of the internal noise commonly associated with standard radio tubes. As a matter of fact, there are number of tubes which are better than Nuvisitors for the front end. But Nuvisitors have caught the public’s fancy.
Sensitivity ratings are given in microvolts on a CB spec sheet, and the lower the rating figure, the more sensitive the receiver