Magellan DIY Instalační příručka stáhnout pdf (Strana 19)

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Possible sources of electrical interference:

• TV or computer cathode ray tube (CRT) displays

• Electric welders

• Air conditioners

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• Brush-type motors

• Electrical Interference

• Relays and switches of all kinds

• Arcing and corona discharge in power line insulators

• Malfunctioning ﬂ ourescent/neon lighting and automobile spark plugs

• Light dimmers

Intermodulation

• Occurs when a strong signal (i.e. communications tower), whose frequency is generally not near that of

• the wireless receiver, overloads some circuit in the receiver As a result, the circuit generates harmonics of the

• strong signal, which then combine in the receiver to create a new frequency

• The newly created frequency, called an Intermodulation Product, interferes with the wireless

• system in much the same way as other sources of interference

• For example, mounting a transmitter too close to a receiver can cause intermodulation. The signal from

• the transmitter is too strong due to its proximity to the receiver

RF Reﬂ ection and Attenuation

• RF Reﬂ ection and Attenuation

• Reﬂ ection: RF signals bounce off a reﬂ ective surfacE such as a wall or the ground

• Attenuation: When RF signals pass through solid objects, some of the signal power is absorbed. Thisloss of RF

energy is called Attenuation, which varies depending on the structure of the object

• An installation site’s physical construction and the obstacles on the site affect RF signals

• Walls, doors, ﬂ oors, elevator shafts, people and other obstacles offer varying degrees of attenuation and reﬂ ection

• This causes the RF radiation pattern to be irregular and unpredictable

• When an RF wave meets an obstacle, one of the following three phenomena occur:

• Reﬂ ection

• Reﬂ ection from walls, ceilings and ﬂ oor surfaces can be partial or complete and cause multipath interference

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Magellan DIY Instalační příručka Strana 19