RECOGNIZING LINK-11 NET PROBLEMS

Figure 5-13.—The Spectrum Display screen of the LMS-11. RECOGNIZING LINK-11 NET PROBLEMS The LMS-11 is very useful in evaluating Link-11 net quality. As you have seen, the various on-line modes can help you determine various problems. These include a station that is consistently missing call-ups, poor signal-to-noise ratio, and low power from a unit. Some common Link-11 problems and the LMS-11 display are covered in the next few paragraphs. Figure 5-14 shows an example of how a PU not responding to call-ups would appear on the LMS-11 operating in the Link Monitor mode. When a PU does not respond to a call-up, the reason may be that the incorrect PU number was entered at the NCS or at the DTS of the unit. It can also be caused by a poor receiver at the PU, causing the PU to not receive its call-up. A third problem could be a weak transmitter at the PU, causing the NCS to not receive the response and therefore, repelling the PU. Figure 5-14.—A PU not responding to NCS call-up. Figure 5-15 shows the display that appears when a PU is responding to NCS call-ups, but the report contains no data. Causes of this problem could be the KG-40 has an alarm, the CDS program is down, or the problem is in the CDS computer to DTS patching. Figure 5-15.—A PU responding with no data. When NCS fails to receive a stop code from a PU, it causes a stoppage of the net, as shown in figure 5-16. If this condition occurs repeatedly and can be traced to a single PU, the NCS should delete the PU until the stop code problem in the DTS is corrected. 5-18