Semi-rigid coaxial cable has a solid outer conductor and is manufactured by drawing seamless tubing over the insulating material and center conductor. It is electrically superior to flexible cable with 100% shielding effectiveness (Figure 9); generally lower loss, extended frequency range, and uniform impedance. Typical outer conductors are aluminum or copper, either of which may be tin-plated. The center conductor is usually solid silver placed copper, which has the advantage of being non-magnetic with loss. Silver plated, copper clad steel center conductor is also available.
Figure 9 - Shielding Effectiveness (Click to enlarge)
A typical flexible coaxial cable has an outer conductor made of fine silver-plated copper wires braided over the insulation material. Other outer conductors use wide silver-plated copper strips braided in a basket weave configuration, or hundred of silver-plated copper wires running parallel to one another in a long spiral. Stranded, flexible center conductors are common in flexible cable. Coaxial cables with stranded center conductor and braided outer conductors are intended for use in applications where the cable must flex repeatedly while in service, but will exhibit higher attenuation as compared to cables with solid center conductors.
Conformable cable is an alternative to semi-rigid or flexible cable. These cables have a center conductor of various types of metallic braid. Standard semi-rigid connectors can be used with conformable cable, and it will retain its shape once bent. performance is generally between semi-rigid and flexible cable.
Table 3 - Typical Cable Specifications
Stainless Steel Cables
SSI’s stainless steel coaxial cable assemblies have 100% reliability rating. These carefully constructed coaxial cable assemblies incorporate a stainless steel jacketed coaxial cable with welded cable/connector interfaces. The additional strength and corrosion resistance of these assemblies is a definite advantage in extreme mechanical or atmospheric environments. Whether during installation or because of environmental stresses, soldered cable/connector failure will result in increased cost through system downtime, fault isolation, and replacement. The stainless steel advantage is is clear.
SSI constructs stainless steel cable by drawing a stainless steel jacket over a thin copper outer conductor. The stainless steel jacket give the cable
- Superior mechanical strength
- Corrosion resistance
- Copper outer conductor provides optimum conductivity
SSI offers stainless steel cable in .093, .145, and .240 inch outer diameters with solid, medium loss, and low loss PTFE dielectrics. Inner conductor substitution of steel in place of copper is also available.
SSI’s stainless steel cable assemblies are made using a GTAW (gas-tungeten-arc weld) cable/connector attachment.
- Many times stronger than the solder joints of other semi-rigid cable assemblies
- GTAW Fusion weld yields a connector joint that is stronger than the original metals being joined
- Torque and tensile strengths are enhanced such that joint failures are virtually eliminate
The welded cable connector joint dramatically improves performance at cryogenic temperatures (below 80 degrees K). Standard soldered joints have a tendency to crack and fail at these low temperatures, but SSI’s welded connections have proven to provide reliable service.
Stresses that are not rejected in a copper assembly are absorbed in the metal as cold working (work hardening), fatigue, and eventual failure of either the copper jacket or the tin-lead solder joint. A stainless steel assembly will experience must less fatigue and failure than a non-ferrous jacketed cable during the common stresses of installation, vibrations, and shock.
Mechanical performance conditions can be difficult to characterize for coaxial cables. The stresses they are subjected to are the result of configuration, tolerances, and dynamic conditions. Many times a cable will meet MIL or industry standards but fail in the system. SSI has performed extensive testing which clearly shows stainless steel cable assemblies as the best choice for mechanical performance.
We back all of our stainless steel coaxial cable assemblies with a five-year warranty. We have never had a return!