Answer
In some installations, stray RF energy can infiltrate audio lines and data lines, causing erratic operation of RoIP devices. Certain modes of radio frequency transmission can be especially prone to causing interference. Pulse type modulation that occurs in cellular TDMA systems, certain types of trunking system modulation, as well as high power transmitters, are common sources of problems.
For example, a typical symptom of this phenomenon is PTT dropout. When the transmitter comes up to full power, it’s controlling IP-223 may drop the PTT, as a result of RF getting into the data stream and corrupting it.
Eliminating locally radiated RF energy is the first step in determining the cause of the problem. Put a dummy load on the transmitter and retest it. If the problem ceases, chances are you have found the problem. Steps can then be taken to eliminate radiation of the RF from cables, nearby antennas, etc.
In this case the antenna was too close to the equipment rack, and once it was mounted further away, the problem disappeared. Similar procedures can identify other sources of radiating RF energy as the cause of the problem. Antenna cables with poor grounds, bad connectors, cables being too close together, etc, can cause simillar problems.
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