PIM Signs For RF Connectors

May 03, 2019
PIM Signs For RF Connectors

PIM often shows poor statistics for affected departments. One of the first and most direct indications of PIM can be seen in a cell with two receive paths. If the noise floor between the two paths is not equal, the reason is likely to be to generate PIM in the noise receiving path. The operator refers to this condition as the reception diversity noise floor imbalance. In this case, the path Rx 0 shared with the transmitter is particularly noisy because the path typically has sufficient power and only some non-linear devices or junctions need to be added.

Sector antenna system with Rx test port

The noise floor on both receive paths can be caused by something external to the antenna system, such as rusted bolts or interference from external sources. In either case, it is worthwhile to analyze the cause. Other more general indications of PIM include shorter calls, lower call rates, and lower call volumes.

Another possible indicator of PIM is a site with frequent performance issues during peak traffic hours, but when a technician investigates, no real failures are discovered. Once the sector is reset or calibrated, it takes some time to establish performance data, and the fault does not become apparent until the sector processes a certain amount of traffic again (usually the next day).

Web sites with more than 12 months of performance problems are often heard. After multiple on-site visits, performing tower tasks, and spending a lot of time and money, the technicians found that the PIM test identified a simple connector nut. On the jump line.

If the cell site does not perform well in the presence of dry conditions, but significantly improves when heavy rain passes through the area, the technician should immediately check the surrounding area for rusted supports such as air conditioning ducts.

This common fault is common in rooftop sites in densely populated areas.