3. General Detail
3.1 Getting The Best From The Test Equipment
There are a number of practices that will allow the best to be gained from the IM test system, especially for taking PIM
measurements.
Connector & Cable Care
• Good quality connectors and test cables are essential for making PIM and return loss measurements
• Take good care of the RF connectors on the test port and the test cable. Do avoid damaging the connectors in transit
• Remove O-rings from all test equipment adapters and test leads. This will reduce the torque required to achieve
a tight, low PIM connection during test and extend the life of the connectors. (Do not remove O-rings from the site
jumper cables)
• Care should be taken when mating a cable to the test port on the test set. Ensure the mating surfaces line-up
correctly, and the coupling nut does not cross thread. Tighten the locking nut by hand initially, and then only do a nal
torque using a spanner. If a torque spanner is used, torque the 7-16 connector to a maximum of 25 Nm; otherwise
ensure that the connector is rmly fastened. DO NOT allow the body of the connector to rotate. DO NOT over-torque
these as this can cause permanent damage to the connector.
• Ensure that the relevant connectors are cleaned regularly as lack of cleanliness can cause PIM problems
• A cleaning kit is supplied within the accessories kit for this purpose. Clean connector mating surfaces using a cotton
bud and an isopropyl wipe to remove dirt, dust & small metal lings
• The connection of the cable screen to the connector is a major cause of PIM problems, so observe connector
assembly instructions closely if constructing your own
• Do not allow the body of the connector to rotate while tightening
• Keep protective caps installed on RF connectors whenever they are not in use
• RF connectors have a nite life and are typically rated for 500 mate / de-mate cycles by connector manufacturers.
Longer life is achievable with proper Care
Making PIM Measurements
• PIM measurements made by the test set are aected by all items attached to the test port. This includes the test
cable, the device under test and any terminations.
• Be aware that high power resistive loads are known to have poor PIM in the region of -60 to -80 dBm for two +43 dBm
tones. Choice of RF load type is important and cable loads are preferred for good PIM performance.
• Not all test cables are suitable for taking good quality PIM measurements.
• All isolators and circulators are known to be a source of poor PIM performance in the region of -50 dBm for two +43
dBm tones.
• If constructing your own cables, the major sources of PIM are in the connectors, the connection of the Outer
Conductor of the coax to the connector and the Outer conductor itself. Observe connector assembly instructions
closely.
• PIM measurement must be taken under conditions that simulate the physical stresses that apply in the installation
environment, and the recorded results can only be regarded as relevant if this stress is applied during the test
sequence. International standard IEC37065 provides guidance on this matter.
General Tips and Caution
• Correctly terminate components to measure best return loss
• When not carrying out measurements, switch the RF Output Power OFF, for safety reasons
• When connecting or disconnecting from the measurement port, switch the RF Output Power OFF
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