Care and Handling of Precision Connectors
Device Specifications
2-4
mechanical wear. They are often found, upon assembly, to be out of
specification. This makes them potentially destructive to any precision 3.5 mm
connectors to which they might be mated.
Use extreme caution when mating SMA connectors with 3.5 mm precision
connectors. Prevent accidental damage due to worn or out-of-specification
SMA connectors. Such connectors can destroy a precision 3.5 mm connector,
even on the first connection.
Hewlett-Packard recommends that you keep three points clearly in mind when
you mate SMA and precision 3.5 mm connectors: SMA inspection, alignment,
and mechanical mismatch.
SMA Inspection
Before mating an SMA connector (even a new one) with a precision 3.5 mm
connector, carefully inspect the SMA connector, both visually and mechanically
with a precision connector gauge designed to measure SMA connectors. A male
SMA connector pin that is too long can smash or break the delicate fingers on
the precision 3.5 mm female connector. Gauging SMA connectors is the most
important step you can take to prevent damaging your equipment.
Alignment
Be careful when aligning the connectors. Push the two connectors together
with the male contact pin precisely concentric with the female. Do not
overtighten or rotate either center conductor. Turn only the outer nut of the
male connector and use a torque wrench (5 lb.in., 60 N-cm) for the final
connection. Note that this torque is less than that when mating precision 3.5
mm connectors with each other. A torque wrench suitable for SMA connectors
preset to 5 lb.in. is available (HP part number 8710-1582, CD 0).
The TDR plug-in modules come with adaptors already installed to prevent
damage to the channel connectors. Then, if accidental damage does occur, the
adapter is all that needs to be replaced. It is easier and cheaper to replace a
damaged adapter than a channel connector. SMA connectors can then be mated
with precision 3.5 mm connectors without difficulty or fear of expensive and
time-consuming repairs.
Mechanical Mismatch
Significant structural and dimensional differences exist between these two
types of connectors. Precision 3.5 mm connectors, also known as APC-3.5
connectors, are air-dielectric devices. Only air exists between the center and
outer conductors. The male or female center conductor is supported by a plastic
"bead" within the connector. In SMA connectors, a plastic dielectric supports
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