Exalt Communications, Inc.
EX-5i Installation & Management
5000005
59
2006-05-17
6.4 Multipath
Propagation
Multipath propagation is a term that encompasses changes to the RF path, such as reflections
and/or refraction, that can cause partial or complete destruction of the radio signal, and thus
excessive bit errors and/or system outages.
Rapid changes in temperature, inversion layers, humidity, air pressure, water evaporation, as
well as standing water or moisture on objects along the path, are all examples of changes that can
cause multipath propagation. New building construction near either end of the path, or along the
path, may cause new reflection characteristics.
If your system has been operating without issue and is suddenly experiencing issues that are
symptomatic of a certain time of day, or related to change in climatic events or some of the
external factors listed above, this is likely the cause.
A professional RF path engineer should be consulted in these cases. Often, minor repositioning
of the antennas at either or both ends may reduce or eliminate these problems.
6.5 RF
Interference
RF interference is usually indicative of another radio system nearby either end of your radio
system, or aimed towards one or both ends of your radio system – usually at or near the same
frequency, and usually a signal level similar to the level of the signal of your own radio system.
Other forms of RF interference also exist, such as electronic equipment that may be placed close
to the radio chassis, or transmitters that may couple onto the cabling or grounding system of the
radio. Microwave ovens and wireless communication devices used nearby the equipment or
cabling are examples of electronic equipment interference.
The EX-5i operates in the 5250 to 5850 MHz band. Wireless Internet devices and
cordless phone technology may also use this frequency band. It may be necessary
to separate the EX-5i chassis, cabling system and antenna from these types of
devices.
RF interference, like most other causes of problems, will be indicated by significant bit errors
and/or system outages.
One means to determine presence of interference is the use of a spectrum analyzer that covers the
same range as the radio system. A professional RF engineer can use a spectrum analyzer to
locate sources of interference, measure these sources, and determine potential remedies that may
be taken to operate in the presence of interference.
If a spectrum analyzer is not available, the radio’s RSL port may be used to determine RSL
levels of interfering signals. By turning the far-end radio off, the residual RSL measured by the
radio indicates the level of interference seen by the radio. It is possible that interference levels
below that which can be measured will still have impact on the radio system – especially if the
radio system has low fade margin or is using a high order modulation.
