APPENDIX A
CARE AND HANDLING OF MICROWAVE COAXIAL ASSEMBLIES
difficult to turn, either the pins are not mated, the coupling nut is cross-threaded, or one of the
connectors has been damaged by excess torque.
Never hold a male connector coupling nut stationary while screwing a female connector into it.
This rotation can erode the plating and damage both the outer interface rim as well as the pin.
If the pins become locked, serious damage can result to both the equipment and the cable
assembly.
ENSURING PROPER CONNECTOR TORQUE
OVERTORQUING
Once connectors have been properly mated, apply only the proper amount of torque.
Overtorquing damages both connectors involved. Also, a connector which has been damaged
by overtorquing, in turn, damages every connector to which it is subsequently mates. It usually
leads to poor system performance as well. Overtorque can cause:
• Bent pins
• Recessed or protruding pins
• Recessed or protruding dielectrics
• Chipped plating
• Damaged coupling threads
• Coupling nut retaining ring damage
• Mushroomed outer interface shells
• Mushroomed pin shoulders
HEX-NUT TYPES
To mate a connector of the hex-nut type, al ways use a torque wrench set to the correct torque
value. Tighten the connector slowly until the wrench snaps. Tightening too quickly can cause
the wrench to exceed its set limit. Do not snap the wrench more than once as this also causes
overtorque.
KNURLED NUTS
Tighten connectors with knurled nuts by hand. If this does not provide sufficient tightness use
a hex-nut connector and torque wrench instead. Never use pliers to tighten a connector.
Table A-2 recommends torque specifications for the various types of connectors.
Table A-2 Connector Torque Recommendations
PROPER CABLE HANDLING
Never exceed the minimum bend radius specified for a cable. Guard against tight bends at the
end of connector strain relief tubing, or at the ends of marker tubing where they may be less
noticeable. Although cable bend may seem slight, the actual radius of the bend at the point of
angular departure may be far smaller than the acceptable radius.
A-5
CONNECTOR TYPE RECOMMENDED TORQUE
7 mm connector with hex nuts
14.0 in/lbs ±1 in/lbs
Type N connector with hex nut
14.0 in/lbs ± 1 in/lbs
SMA connector
7.5 in/lbs ±0.5 in/lbs
WPM
7.5 in/lbs ±0.5 in/lbs
WPM-3
7.5 in/lbs ±0.5 in/lbs
WPM-4
7.5 in/lbs ±0.5 in/lbs
Type N connector (knurled)
hand-tight
TNC connector (knurled)
hand-tight
BNC
hand-tight
