Semi Rigid

General

  • Semi-Rigid cables are mainly used for applications in high frequency bands
     ( up to 110GHz ).
  • Semi-Rigid cable is unique that it is easily bent to finished shape and still maintains its set after bending. This property makes it ideal for use with automated bending equipment as well as hand forming.
  • Our vendors are qualified to MIL-DTL-17 and is listed on the Qualified Products List of the U.S Defense Logistics Agency.
  • Available cable diameters range from .020inch to .500 inch.
  • Available impedance range from 10 Ohms to 100 Ohms
  • A very special advantage is the 100% shielding with low VSWR

Core Competence

  • Semi-Rigid Coaxial Cable
  • Mil-DTL-17 QPL Approved Cable
  • Special Impedance Cables
  • Low Attenuation Cables and Assemblies
  • Hand Formable Cable and Assemblies
  • Delay Lines
  • Cable Assemblies
  • Build to Print Cable Assemblies
  • Phase Matching
  • Balun / Transformers
  • Stripped and Formed Semi-Rigid Cables

Products

Microwave Cabel Assemblies:

We distribute microwave cable assemblies from 1 GHz up to 110 GHz.

Semi Rigid Cables:

Everything you need to know about Semi Rigid Cables.

Coaxial Cables:

Standardized Coaxial Cables that are held on stock and therefore available in 3-5 work days.

MIL-DTL-17 QPL

  • Our diverse range of 27 QPL cables includes copper and aluminum jacketed cables in sizes of .034, .047, .086, .141 and .250 diameters.
  • These are available un-plated or with silver, tin, or tin-lead plating

We will help you to archive your goals!

Markets and Products

Mil / Aero:

  • Mil-DTL-17-QPL listed cables
  • Aluminum Jacketed Cables
  • Low Loss Cables and Assemblies
  • Phase Matched Cable Assemblies
  • Hand Formable Cable and Assemblies

Industrial:

  • Coaxial Balun / Transformer assemblies
  • Stripped and Formed Semi-Rigid cables
  • Special Impedance Cables
  • High Power Cable and Assemblies

Medical:

  • Non Magnetic Connectors and Assemblies
  • Special Impedance Cables
  • Stripped and Formed Semi-Rigid Cable

Academic / Accelerator:

  • Non Magnetic Connectors and Assemblies
  • Hand Formable Cable and Assemblies
  • Phase Matched Cable Assemblies
  • Stainless steel cable and cable assemblies

Test and Measurement:

  • Precision test cables RG401, RG402, RG405
  • Low Loss Cables and Assemblies
  • SMP Cable Assemblies
  • E-FLEX 40G Assemblies
  • E-FLEX 40G Hand Formable Cable Assemblies
  • High Power Cable

Center Conductor

  • The center conductor is either a solid or stranded metal wire which acts as the primary electrical signal carrier for any coaxial cable. Most attenuation occurs at the surface of the center conductor due to the „skin effect“ of microwave signals making the finish or plating a very important element. Stranded center conductors are generally only used in flexible cable constructions for added flexibility and longer flex life. In comparison, solid center conductors have lower attenuation and tend to be more amplitude stable with flexure while stranded center conductors tend to be more phase stable with flexure. For larger Semi-Rigid cables, a tubular center conductor can be substituted. The tubular center conductor reduces weight and thermal conductivity without any impact to the electrical performance.
  • Silver plated copper (SPC) per ASTM B-298 and silver plated copper clad steel, also referred to as silver plated copper weld (SPCW) per ASTM B-501, are the two most common center conductor materials. Silver plating, besides being an excellent electrical conductor, prevents oxidization during manufacture and improves the solderability of the finished cable. Stainless steel and beryllium copper are also used when low thermal conductivity is a priority. Other materials, including many copper alloys are available on special request.

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Dielectric

  • The insulating material between the center and outer conductor maintains the spacing and geometry of the cable and ensures mechanical integrity during forming and bending. Most transmission losses are caused either directly or indirectly by the dielectric. Cables with a low dielectric constant, while offering lower bulk dielectric losses, also require a larger center conductor diameter to maintain the same characteristic impedance. The larger center conductor can significantly lower the overall cable attenuation. In addition, the dielectric determines the velocity of propagation, temperature range, power rating, phase and amplitude stability, and contributes to cable flexibility.
  • The most commonly used dielectric for high performance microwave coaxial cable is Polytetrafluorethylene (PTFE), in both full density and low density (a.k.a. low loss or micro-porous) forms. PTFE is an excellent choice for a cable dielectric due to its low reactivity to chemicals, an operating temperature that can withstand the heat of soldering.

Outer Conductor

  • The outer conductor serves many purposes. It is the electrical shield which contributes to cable attenuation and controls RF leakage. Through precision mechanical tolerances, the outer conductor minimizes return loss (VSWR) by maintaining a constant characteristic impedance. The outer conductor is the primary strength member that keeps connectors firmly attached to the cable. It often provides environmental protection and determines the flexibility or how easy the cable can be formed or bent. The most commonly used materials can be in many forms such as tube for Semi-Rigid cable, tin coated braid for conformable cables, or a foil in high performance flexible cables. Material selection typically involves trade-offs between electrical performance, size, and flexibility.

How to use a Semi-Rigid Coaxial Cable

  • The electro-mechanical performance specified for Semi-Rigid Cables is achieved by a compression fit between the outer conductor and the dielectric core which, in turn, necessitates manufacturing processes that cause deformation of the core by compression and elongation. The resulting stress that is initially non-uniform tends to equalize by cold flow within a few weeks after manufacturing, and will cause withdrawal of the core into the cable. If this occurs in cable that has become part of a cable assembly, the resultant development of an air-void of the cable-connector interface may cause VSWR increases. It is therefore advantageous to achieve core stress relief by preconditioning cable before it becomes a cable assembly.
  • Preconditioning is not effective on long lengths of cable. Bending of cable, which is usually involved with the manufacture of cable assemblies, tends to introduce non-uniform core stresses; therefore, CarlisleIT recommends preconditioning after bending and before attaching the connectors. Since preconditioning will result in the withdrawal of the dielectric into the cable, preparation of the cable assembly should allow for a ¼ inch length on each cable end beyond the design dimension. The outer conductor and the core should not be cut to the final dimensions until preconditioning has been completed.

Preconditioning Procedure

  • A recommended preconditioning procedure consists of three cycles of the following routing:
    1. Heat the specimen to the maximum operating temperature. Maintain at temperature for one hour minimum.
    2. Return specimen to room ambient temperature. Trim protruding core, if any, flush with the edge of the outer conductor.
    3. Maintain specimen at room temperature for one hour minimum.
    4. Cool specimen to -45°C and maintain for one hour minimum.
    5. Return specimen to room temperature and maintain for one hour minimum.
  • After the last temperature cycle, maintain the specimen at room temperature for 24 hours minimum before proceeding with further processing.
  • Important is to test the cable in your assembly condition before you produce the cable assemblies.

Fabrication Techniques

Cable cutting

  • Cables having conductors of copper and aluminum are readily cut using circular saws equipped with metal cut­ ting blades of high speed steel or cobalt steel. There are several table-top machines commercially available for this specific task. Special cutting techniques may be required for conductors of copper-clad steel, stainless steel or copper alloys. Abrasive cutoff wheels of suitable thickness (.010" to .062") usually will suffice, although burr removal may be necessary.
  • Dry cutting is preferable to cutting using fluid cooling or lubrication to prevent possible wicking of the fluids into the cable ends

Fabrication Techniques

Stripping outer conductor :

  • Sections of solid tubular outer conductors can be re­ moved by making a circumferential score or scribe mark and breaking the conductor at this mark. (This is similar to the cutting of glass, scribing a line and breaking it on that line.) The scribe line should be of proper depth, singular and the ends should meet together. This prevents a "step" on the broken edge. The edge must then be rolled between two hard surfaces to minimize the burr on the O.D. of the conductor edge. A lathe or a modified rotary wire stripper can be used for scoring the conductor. Do not penetrate into the Teflon while scoring since this would cause the outer conductor edge to be rolled into the dielectric, resulting in an electrical discontinuity at that point.  If done properly, the edge will have only slight irregularities and will provide satisfactory electrical performance for non-critical ap­ plications.
  • Cutting the outer conductor with a rotating blade saw or jewelers saw will require subsequent facing operations and careful removal of any chips imbedded in the dielectric. This method is not recommended for ap­ plications which require superior electrical performance. Removal of the section of outer conductor which has been scribed off is accomplished by quickly breaking at the line (similar to snapping a piece of glass) by flexing in two opposite directions.
  • Do not flex too far since this wil l result in distortion of the conductor edge. The piece can then be pulled off with pliers. Care should be taken not to deform the dielectric by apply ing too much pressure. lf a flush strip to the center conductor is re­ quired here, a razor blade can be used to cut the dielec­ tric. A twist wi l l remove both conductor and dielectric simult aneously (refer to " Trimming dielectric" ). When cutting the dielectric it is important to have a guide to limit penetration, thus avoiding damage to the center conductor. Such damage would not only affect electrical performance but any mechanical Stresses during  subsequent fabrication or operating conditions could cause the conductor to break.

Fabrication Techniques

Forming or bending: 

  • A suitable fixture should be used for forming, one having a clamping arrangement for the cable and a mandrel of appropriate dimensions. An ideal mandrel should be grooved to allow the cable to nest thereby avoiding flattening. The tool used to bend the cable should also be grooved so that the cable is completely captivated at the bend tangent point. Large diameter bends may be made on flat mandrels with little or no deformation occuring. Dedicated tooling may be required because of form complexity but automated or semi-automated universally programmed machines are available which will allow versatility and high production capabiIities.
  • To avoid wrinkling the cable in the bend area, pressure must be applied against the cable at the bend tangent point , forcing the cable against the mandrel. Too much pressure will cause a bulge in the outer conductor at the end of the bend area on the inside. The cable will have a slight amount of "spring-back;' requiring the mandrel to be slightly smaller than the specified bend. This is not a predictable behavior so some experimentation is necessary (usually the larger the bend, the greater the spring-back). These cables should not be formed smaller than the " Safe bend radius" specified in this catalog (see tables). Otherwise, severe electrical and mechanical degradation will occur.

About us

Read more about our company and activity

We are a specialist for innovative and high quality cables solutions and connectors in the area of radio frequency, with a core competence up to 110 GHz.

We offer customized solutions for our customers for 35 years. With our strong international partners, such as Teledyne Storm Microwave, elspec achieves to lead the market and is able to react to ever change of market needs. It doesn’t matter rather it revolves around standard cable assemblies or customized solutions for the specific needs of our customers – elspec works with great experience and technical know-how to find the perfect solution.

With its own factory in Bavaria, we are equipped with excellent machinery. We are also the Value Added Reseller for Teledyne Storm Microwave cable assemblies for Germany, Switzerland and Austria.

 

Standardised Cables, Quality Assurance &
Performing Measurements

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Our simple ordering process and strong customer service assures help as fast
as possible.

Our Cables are being used in a variety of applications


Aerospace, Military & Space


Telecommunication & Industry


Accelerators & Research


Medicine