User's Manual

Exalt Installation and Management Guide
ExtendAir
®
(TDD) Series Direct Mount Digital Microwave Radios
84 000000-001
2011-08-26
RF interference, like most other causes of problems, is 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 to take to operate in the
presence of interference.
If a spectrum analyzer is not available, the radio’s RSL port can help 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 still have an impact on the radio system – especially if the radio system has low fade
margin or is using a high order modulation.
Exalt Digital Microwave Radios provides considerable flexibility to tune to different frequencies
across the bands within which they operate. This is the easiest method to use to try to avoid existing
interference. In addition, the occupied bandwidth of the radio can be reduced. This, along with re-
tuning, can be very effective, however throughput is reduced.
Repositioning the antenna and/or changing polarization, or upgrading the antenna to a higher gain,
and/or using a high-performance antenna, are all secondary means that can be used. It may be
necessary to perform combinations of both radio changes (retuning, occupied bandwidth reduction)
and antenna system changes (position, polarization, upgrade).
Path Obstruction
A path obstruction is defined as an object, such as a building or tree, impeding the proper path of the
radio system. If the system design was proper at the time of installation and issues arise at a later date,
an updated path profile and survey may be necessary to identify changes in path clearance.
Misaligned Antenna
At the time of initial installation, it is critical that the antennas at each end are properly aligned and that
the designed RSL is achieved. However, antennas may become misaligned due to high winds, changes
in the guy-wiring systems keeping the antenna mast stable, or loosening of the antenna mounting
hardware. A reduction in the RSL of the link is symptomatic of this condition, but this condition is not
the only condition that results in a reduction of RSL. However, if conditions occur where the antenna
alignment may be suspected, the mechanics must be inspected and the antennas realigned.
Faulty Antenna (connectorized antenna rc-models only)
A faulty antenna is rare, but is still a possibility. In some cases, the mechanics of the antenna feed can
get moisture inside, or a bad or weak connection in the pin and connector structure of the antenna may
occur. A VSWR measurement of the antenna connection can be made to verify this condition.
Improper Grounding
In addition to being a potential human safety issue, improper system grounding is a somewhat
common condition that can cause continuous bit errors or bit errors when metal objects come in
Note: Exalt Digital Microwave Radios operate in license-exempt bands. Microwave ovens,
wireless Internet devices and cordless phone technology may also use this frequency band. It
may be necessary to separate the radio chassis, cabling system and antenna from these
devices.