User Manual Part 2

Lynx.GX Installation and Management
Use of a Spectrum Analyzer to Evaluate Potential Interference
Connecting to the antenna and using “peak hold” on a spectrum analyzer, the spectrum across the receive
frequency range of the radio can be swept and any signals being received at levels above the radio's specified
threshold identified.
If potential interfering signals are found, you can change the frequency plan to avoid a receive channel that may
contain significant interference (see “Changing Frequency Plans on page 93. For example, you can reduce
interference by moving or swapping terminals. Signals outside the receiver frequency range can be generally
ignored: they almost always do not cause interference.
When using an external spectrum analyzer for determining the presence of interference, use very narrow
resolution bandwidth settings to detect signals down to the unit’s threshold (approximately -80 dBm, depending
upon the type of radio). Use a directional antenna in combination with the spectrum analyzer and determine not
only the frequency, but also the primary direction and the dominant polarization of interference sources. Once
the frequency, direction, and dominant polarization of interference is known, proper planning for your radio
system’s channel plan, polarization, and antenna placement can be optimized.
TROUBLESHOOTING ALARMS
Use these troubleshooting guidelines when you receive:
▪ Data Stream Errors
▪ RF Link Alarms
▪ RF Unit, Cable, IDU Alarms
▪ Far End Alarms
Data Stream Errors
When the radio is in service, errors in the user data may occur. This is usually known to the operator either by
faulty data indications of downstream equipment or by external bit error rate testing. It is possible that no alarms
appear on the front panel during normal operations, even when there are errors present in the data stream.
Some errors do not result in an alarm (such as bipolar violations, improperly terminated connections, or certain
incorrect settings), but are exhibited on downstream data processing equipment or during a BER test.
In other cases, there may be data errors due to atmospheric conditions (fading), interference, or other reasons,
but not at a high enough error level to be indicated with the BER alarm LED. In the case of these types of
errors, the following information can be helpful to troubleshoot the radio link.
Indications
▪ During external BER test, test equipment indicates errors
▪ Downstream equipment (multiplexer, channel bank, codec, router, and so on) indicates errors
Possible Causes
▪ Path fading due to atmospheric conditions
▪ Poor transmission line connections
▪ Antenna problems, misalignment or path clearance
▪ Received signal level (RSL) is too strong
▪ Far-end radio transmitter circuitry is faulty
▪ Near-end radio receiver circuitry is faulty
▪ Interference
Appendix G. Troubleshooting 95