This document provides questions and answers for wireless
A. Locate the source of the interference. In order to do so, look around
at both ends of your link. Do you see any other antennas or related equipment?
If you identify other nearby radio equipment, try to learn:
Who operates it
Who owns it
What frequency or frequencies it operates on
With how much power does this other equipment
What kind or type of antenna polarization is in
See if you can contact the owner or operator of this other equipment to
When you have confirmed the type and location (and other details) of
the interfering radio equipment, you can figure out a solution. Start with your
Change the polarization of your antennas to be opposite (crossed) to
the polarization of the interfering system in order to solve the problem. You
must first ensure that your systems antennas are cross-polarized to the other
systems antennas, because this solution is so effective and requires the least
cost and effort to implement.
If the problem persists, change the frequency of one of the systems
(probably your own). Systems that are not on (or close to being on) the same
frequency rarely interfere with each other. If the interferer is very
high-powered (such as radar), interference can still occur because the powerful
interferer overloads the receiver, and causes interference-like symptoms.
Change of frequencies is usually effective.
Note: This solution is only appropriate in the case of systems that operate
in unlicensed bands, where the use of a specific frequency is not necessary.
This solution option is typically not available to licensed users, although
such users are not likely to encounter interference that they can solve this
Sometimes, you need to change frequencies for both your system and the
interfering system, in order to maximize the frequency separation.
In order to change the frequency of your system, swap the transmit and
receive frequencies. This process requires removal and reinstallation of both
of your duplexers, in order to turn them around to accommodate the now-reversed
TX/RX frequency split. You do not need to make any other adjustment or
re-alignment of the antennas. You can try this when you experience interference
at only one end of your link (the most common situation), because the link end
where the receiver was receiving interference now transmits on that frequency.
In other words, only receivers can experience interference!
You must use the final tool to alleviate an interference problem only
after you have unsuccessfully tried all the others. That tool is antenna gain.
For antennas, higher gain is virtually synonymous with narrower beamwidth. When
you change antennas to higher-gain, lower-beamwidth types your system becomes
less able to see the interferer, and this step sometimes solves the problem.
Note: Usually only one end of a link experiences interference. Therefore,
you only need to change the antenna at the link end where the receiver
experiences the problem. Changing antennas is the most costly and
time-consuming solution. Therefore, install antennas of adequate gain (narrow
If you decide to replace one or both antennas with higher gain units,
verify that the TX power needs to be adjusted downward to ensure that the
radiated TX power (EIRP) still complies with the applicable FCC rules.