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Short-distance interference is a high-frequent interference of the radio reception; it occurs, when undesirable electromagnetic oscillations in the high-frequent reception channel of a radio reception antenna system or of a radio receiver, are received together with the useful signal via the antenna, or, the antenna input at the device, and affect the reproduction of the useful signal in a perceptible way.
Short-distance interferences can be conduction-guided or received by the vehicle's own antenna. For the conduction-guided interferences, a degree of suppression concerning the frequency ranges long wave, medium wave, short wave and ultra short wave is required. For interferences received via antenna, the admissible interference voltage levels are given regarding the reception ranges (long wave - ultra-short wave and portable radio sets). A difference is made between wide-band interference sources and narrow-band interference sources.
Figure 51: Structure of short-distance interference suppression
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