Coaxial Cable Types:  Choose the Right one According to Your Need

FACTS CHECKED BY  Jose George​

All modern homes have at least one coaxial wire wall socket because most companies use coaxial cable for cable television. However, there are so many coaxial cable types available in the market. You must pick the right one which can serve your purpose. So, let’s learn some basics.      

Coaxial Cable Understanding

A coaxial cable or coax cable is an electrical cable where a concentric conducting shield surrounds the inner conductor. The shielded cables got their name coaxial because their inner conductor layer and outer shield share the same geometric axis.

These cables are transmission lines that carry video signals with low losses. You can use it in telephone trunk lines, high-speed computer data busses, cable TV connections, and broadband internet networking for connecting receivers and radio transmitters to antennas. Cables and connectors’ dimensions create precise conductor spacing to work efficiently as a transmission line.

The characteristic impedance of most coaxial cables is either 50,52,75, or 93 ohms. In addition, they have standard type names given by RF Industry. In homes, we mainly use RG-6

RG# or RG#/U was used during World War II. You can find them in MIL-HDBK-216, published in 1962. However, these designations are fading away with time. Currently, the military standards use SPEC MIL-C-17. However, RG-series have become so common that people still use them, but you should not rely on the physical and electrical characteristics of the RG-# type. You can use the RG designation to identify the connectors compatible with the different coaxial cables.

coaxial cable with BNC connectors

Image: coaxial cable with BNC connectors

Types of Coaxial Cable

Let’s understand in detail about types of coaxial cable.

Hardline Cable

Hardline cable usages are in broadcasting and other radio communication applications. THardline cables are suitable for high-strength signal transmission. The central conductor comprises solid copper or aluminum with copper plating and is a larger conductor than others. Its shield may include round copper, gold/silver tube, or a fusion of such different metals. Most hardline RF coaxial cables use a PVC jacket outdoors or for external chassis.  However, there is no need for this insulation jacket in some inside applications. Hardline can be pretty thick,  with the least thickness of half an inch/13 mm. They may be several times thick and have slight losses at high currents.

Radiating Coaxial Cable

Radiating coaxial cable usages are shafts of the elevator, underground transportation tunnels, Navy ships, and other places with no antenna connections. It is similar to hardlines but cut into the shield with tuning slots. You can tune these slots to a specific radio frequency or wavelength of operation. A radiating cable assists in creating a “desired leakage impact” between the receiver and transmitter.

Triaxial Cable

A triaxial cable is a type of cable with three layers of insulation, shielding, and sheathing. The core provides signal and power connections, with the power return supplied through the inner screen. 

An extra shield in the shape of a copper braid distinguishes the triaxial cable. The interior conductive parts of the cable are protected from capacitive field noise and ground loop currents by this grounded braid. Furthermore, as the triaxial cable has higher bandwidth and better interference rejection, it’s excellent for applications with strong electromagnetic fields. It also effectively lowers cable loading and cable losses. The most prevalent application of triaxial cable is in cable television. It’s also used to connect cameras to their central processing units (camera control unit).

Twin-axial Cable

Twin-axial cables are balanced, twisted pair cables within a cylindrical shield. It permits a nearly perfect differential mode signal to pass through, insulated and balanced. Unlike the standard coaxial cables with a single conductor, a twisted pair cable has two conductors in the center enclosed in a single-layer outer core. Twisted pair cables offer several advantages like lesser cable loss, better shielding from capacitive effect and ground loops, and lesser magnetic noise of low frequency. These connections are ideal for low-frequency digital and video applications.

RG-6 Cable

Four types of RG-6 cables suit different applications. The inner conductor is either CCS (copper-covered steel) or solid copper. 

Among these four types, “Plain” (also called “house”) is suitable for indoor applications. It can give off poisonous gas when burned due to its outer plastic covering. 

You can use “flooded” cables in direct burial or underground conduits; they have water-blocking gel. 

The messenger cable also has waterproofing, but it is different from flooded as it has steel wire to prevent it from hanging down a utility pole.

Lastly, the plenum cable, the most expensive among all, has a Teflon outer jacket to meet mandatory fire codes. Due to this feature, you can use it in ventilation ducts.

Semi-Rigid Coaxial Cable

Semi-rigid cables have an outer sheath of solid copper instead of a braided sheath. As a result, this coax provides better screening, specifically at high frequencies. However, these cables do not have much flexibility and do not flex after initial formation.

 This cable type is not too flexible and does not flex after initial formation.

Rigid Line

A rigid coaxial cable has dual copper tubes kept concentric. It would help if you had elbows for turns as you cannot bend the rigid lines. PTFE supports help to keep them in their place. You can use inner support or a connection kit/flange to join the stiff line. You can use a rigid line to link RF components and high voltage transmitters indoors, but for outside, you will need a more durable and flanged rigid line on an antenna mast and other RF components. The outside line on antenna masts and other similar structures is sometimes made of aluminum to save weight and money, but it needs extra care to avert corrosion.

Formable Coaxial Cable

A formable or conformable cable is an alternative to a semi-rigid coaxial wire. Instead of a rigid copper outer sheath, a flexible metal sheath is used to match any cable configuration without special tools. Prototype applications can use coax cable to lay out the cable placement designs. Once the cable becomes stable, you can modify the design to use a semi-rigid coaxial cable.

comparison of common cable

Image: comparison of common cable

Factors to Consider While Selecting a Coaxial Cable

The radio guide (RG) number on a coaxial cable doesn’t always tell the whole picture; there are several additional aspects to consider when choosing a cable for your specific application.

Application

Certain types are developed for specific tasks, such as military signal transmission, while others are intended for general usage. Consider whether your application necessitates short- or long-range transmission and high- or low-frequency transmission.

Impedance

Impedance is the resistance of an electrical circuit to alternating currents, measured in ohms. To avoid echoes, signal attenuation, and ghosting television images, all components of a coaxial cable system should have the same impedance.

Environment

Underground cables must pass through watertight pipes to prevent infiltration of liquid and vapor into their jackets. You can also use waterproof cords with self-amalgamating tape. Some manufacturers also use hardened polyethylene cables or cables with tin and silver coatings to give protection from sunlight and corrosive gas.

Working Voltage and Power Rating

Voltage goes through the central wire or conductor of a coaxial cable. Calculate a maximum or “peak” voltage for each cable, which is significantly reduced as a safety precaution.

Signal Loss

Signal loss in coaxial cable lines can occur at very high frequencies (VHF) and ultra-high frequencies (UHF). For VHF and UHF interference prevention, some manufacturers include a foil or braided barrier.

coaxial radio frequency cable

Image: coaxial radio frequency cable

Conclusion

Different types of coaxial cables are available based on several factors such as application, construction, layer pattern, and material used. Users should inspect the cables’ design to reduce signal interference and troubleshoot issues. We are a customized wire harness manufacturer with our factory, and we can give you alternative products to decrease your overall cost and delivery time.

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