CABLE AND HARNESS
COAXIAL
coaxial cables and attachments
COAXIAL

Coaxial is an engineered cable product, typically supplied in the form of a central conductor insulated by a dielectric material, held in concentric orientation to a conductive tubing or sheathing that serves both as an EMI/RFI shield and as a return circuit path.

Coaxial systems are available in different technologies, ranging from flexible, insulated cable; to semi-rigid and rigid metallic sheathed.

The selection of a particular coaxial cable technology involves the careful consideration of the specific electrical, mechanical and environmental requirements of the project.

flexible cable rigid cable

PREFERRED

FLEXIBLE CABLE

Cable dimensions and layout meet design requirements, with smooth bends and sufficient stress relief. Connector backshell is properly assembled and torqued. Cable insulation jacket is smooth and continuous, shield properly secured.

NASA-STD-8739.4 [19.6.1.f]

PREFERRED

SEMI-RIGID/RIGID CABLE

Completed cable meets dimensional and layout requirements, with smooth surface, bends, uniform diameter and sufficient stress relief. Connectors exhibit properly formed solder/weld fillets and are contamination/corrosion-free.

NASA-STD-8739.4 [19.6.1.f]

cable terminus alignment painted cable assembly

MANDATORY

CABLE TERMINUS ALIGNMENT

A minimum straight length of six (6) cable diameters is required at each finished cable end to allow for clearance and strain relief, unless specified otherwise in the engineering documentation.

Best Workmanship Practice

MANDATORY

COATING/FINISH

In applications requiring the cable assembly to be coated or painted, the finish shall be applied to the outer sheath only, and shall stop at least 5 mm (0.20 in.) from the back of the connector. The connector shall not be coated or painted.

Best Workmanship Practice

NASA WORKMANSHIP STANDARDS
NASA logo Released:
04.05.2002
Revision:
Revision Date:
Book:
4
Section:
4.04
Page:
1




CABLE AND HARNESS
COAXIAL (cont.)
floating nuts minimum bend radius

MANDATORY

FLOATING NUTS

Semi-rigid/rigid cable assemblies shall be designed with connectors with retractable (non-captive/floating) coupling nuts, reducing the possiblity that the cable assembly will be in a state of tension/torsion during connector mating.

Best Workmanship Practice

MANDATORY

MINIMUM BEND RADIUS

Coaxial cables shall not be bent below the minimum recommended inside bend radius (6 diameters for flexible, 2 diameters for semi-rigid and rigid).

Best Workmanship Practice

excess solder on solder termination between a connector and a cable sheath improper assembly of center contacts

UNACCEPTABLE

EXCESS/IMPROPER SOLDER

The solder termination between the connector and the rigid/semi-rigid cable sheath shall exhibit a fully wetted, concave, smooth and continuous fillet which extends completely around the termination periphery.

Best Workmanship Practice

UNACCEPTABLE

IMPROPER ASSEMBLY
CENTER CONTACT(S)

Center contact location/orientation does not meet requirements for proper mating.

NASA-STD-8739.4 [19.6.2.f.3]

improper assembly connector improper bend radius

UNACCEPTABLE

IMPROPER ASSEMBLY
CONNECTOR

The connector has not been assembled per the manufacturer's or engineering documentation. The connector body has been crimped by the center pin crimp tool, crushing the dielectric.

NASA-STD-8739.4 [19.6.2.f]

UNACCEPTABLE

IMPROPER BEND RADIUS

The cable has been bent below the minimum radius recommended, resulting in ripples and stretching in the cable sheath and possible cold-flow of the dielectric, resulting in increased attenuation and/or shorting.

Best Workmanship Practice

NASA WORKMANSHIP STANDARDS
NASA logo Released:
04.05.2002
Revision:
Revision Date:
Book:
4
Section:
4.04
Page:
2




CABLE AND HARNESS
COAXIAL (cont.)
improper coating improper terminus spacing

UNACCEPTABLE

IMPROPER COATING/PAINT

The coating has been improperly applied, resulting in interference during assembly and mating.

Best Workmanship Practice

UNACCEPTABLE

IMPROPER TERMINUS SPACING

The termination exhibits an improper minimum straight section length between the connector body and start of nearest bend. This may impede assembly/mating, reduce strain relief or increase cable impedance.

Best Workmanship Practice

protruding dielectric

UNACCEPTABLE

PROTRUDING DIELECTRIC

Care shall be exercised to minimize the protrusion or melting of the dielectric as a result of overheating during tinning and soldering operations.

Best Workmanship Practice








NASA WORKMANSHIP STANDARDS
NASA logo Released:
04.05.2002
Revision:
Revision Date:
Book:
4
Section:
4.04
Page:
3





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