Guide to Different Types of Coaxial Cables

To answer that, we will have to talk about the coaxial cable first. What it is, where it is generally used, and its specific benefits. Then we can talk about the different types of coaxial cable. 

Coaxial Cable - A Brief

They are a cable that transmits electric signals between devices and systems. These cables specifically pass radio frequency signals in the form of transverse electromagnetic waves. 

By design, there is an inner conductor, surrounding which there is a dielectric layer; this layer is enclosed in a cylindrical sandwich with additional layers of shielding and an outer protective jacket to prevent damage to the signal carrying component during installation or from the environment. 

Coaxial cables can transmit high-frequency signals with less loss. 

Different Types Of Coaxial Cables

There are different types available, all suited for their specific purpose. Let's take a look:

- Hard line coaxial cable

- Flexible coaxial cable

- Semi-rigid coaxial cable

- Formable coaxial cable

- Rigid coaxial cable

- Twin axial cable

- Triaxial cable

Hard Line Coaxial Cable

Hard line coaxial cables can be used for high strength signal transmission. This cable uses a center conductor made out of copper, silver, aluminum, or steel. It is larger in diameter than fellow coaxial cables. To prevent arcing and as an inhibitor to moisture, some hard-line cables make use of pressurized nitrogen. 

Flexible Coaxial Cable

As is in the name, Flexible coaxial cables can flex according to the requirement of the situation. Flexible coaxial cables use a metal inner conductor surrounded by a flexible -- dielectric -- polymer with an outer jacket. 

To increase flexibility, the metal conductor can be changed to a stranded design from a solid wire, and a polyethylene (PE) dielectric foam can be used instead of the rigid dielectric material. 

Flexible coaxial cables are most commonly used for home video equipment and televisions. 

Semi-Rigid Coaxial Cable

Semi-rigid coaxial cable uses a solid copper outer sheath with a dielectric of PTFE. The copper provides superior shielding, and the dielectric properties have enhanced high-frequency performance. There are limitations to how you can flex this cable once it is formed. 

Formable Coaxial Cable

Again, as the name suggests, this one is a little more flexible and adaptable. A flexible metal sheath is used so it can be reshaped and reformed to meet the needed configuration. Formable coaxial cable can sometimes be used to lay out the design for cable placement in prototype applications; once the design is set, the application can use the semi-rigid coaxial cable in the final version. 

Rigid Coaxial Cable

The name, Rigid coaxial transmission line, fits well as it was meant to be flexible. The rigid coaxial cable has two concentrically mounted copper tubes, supported at fixed intervals across the length of the cable with PTFE supports or disk insulators. Rigid transmission lines are manufactured in flanged straight sections of fixed lengths. So you can get 45- or 90-degree elbows to join sections of the transmission lines. There are specialized braces and springs for differential expansion and contractions of the inner and outer copper tubes in the transmission line run. 

Twin Axial Cable

Twinax cables are best for low-frequency digital and video applications. Also known as Twinax, it can have two central conductors in the core with a single outer core and a dielectric. This cable has certain advantages, like reduced cable loss, more protection from ground loops, capacitive fields, and lesser low-frequency magnetic noise. 

Triaxial Cable

Known as Triax, it is so called because it has an additional copper braid added to it. It works as a shield and is grounded, thus passing any ground loop currents or capacitive field noise away from the inner core conductive elements. 

The Triax cable provides more bandwidth and interference rejection, improves the signal-to-noise ratio, and reduces cable losses and cable loading. 

How To Specify Coaxial Cable

Many factors specify a coaxial cable, from the inner conductor to its RG (Radio Guide) type -- for example, the RG6 coaxial cable is commonly used for home video applications.

Another thing that plays a role in identifying the type is the material of the inner conductor - silver-coated copper, copper, tinner copper, or aluminum/copper. 

Then there is the jacket material - which is chosen based on the usage and the environment's wear and tear.