How the latest spectrum analysers help engineers to troubleshoot radio interference problems: Page 2 of 5

July 29, 2013 //By Anritsu Company
The exploding growth of wireless services has made interference – once uncommon – a fact of life for wireless and broadcast professionals. For example, a metropolitan area of approximately one million people may have 1,000 licensed two-way radios, 600 cell sites, and 100 broadcasters.
envelope. If the spectrum analyzer has spectrogram capability, it can be used to check for periodicity. For signals that are intermittent with a long time between appearances, it can be helpful to use a “Save on Event” capability. This capability uses a mask automatically generated from the “normal” signal and only saves a trace when something unusual appears. Once saved, the traces can be examined for time-of-appearance and signal characteristics. The burst detect feature in many Anritsu handheld spectrum analyzers is very useful when hunting for bursty signals, especially ones that occur with a low duty cycle.

While looking for signals that don’t belong on the input to a receiver, it’s important to know what signals are typically present in the bands, as well as what other legitimate signals may be present. This can save much time when hunting signals. If this is not possible, the signal can be demodulated so the user can listen for the station ID call sign.

Many interfering signals are not so easy to identify, so field engineers must find them by hunting. Possible interference causes to seek are on-channel interference, in-band interference, impulse noise, harmonics, passive intermodulation (PIM), or intentional interference caused by a jammer.

Locating the source of interference

Once an interfering signal has been spotted and characterized using the tower’s antenna, the next task is to find the same signal using a ground level antenna. This will allow the field engineer to search for the signal, either by direction finding or seeking areas of higher signal strength. One issue is that signals that may be strong atop the tower may be weak at ground level.

Initially, it must be determined if the signal is visible near the tower base. If it is, the signal has been spotted at ground level and it’s time to move to the next task, locating the source. If not, there are several things to attempt:

  1. Check other
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