New advancements in technology are slowly wiping out what we once deemed as “amazing” in the tech field. Bluetooth, for instance, left many in amazement a few years back, but currently, Wi-Fi seems to be taking over in almost all aspects of wireless communication. While technology is indeed changing everything, scientists seem to have had a hard time shaking off coaxial/coax cables.

You’ve probably seen them before on cable TV, or on satellites. However, not many people really understand what goes on in a coax cable and even what’s inside the sheath.

Inside The Coax Cable

The outer plastic sheath that you see on a coax cable covers three components inside it including: 
- Copper core
- Dielectric insulator
- Copper shield

Typically, the copper core is responsible for conducting actual electrical signals across the cable. On the other hand, the copper shield and the dielectric insulator reduce magnetic interference in the cable.

Signal Transmission in a Coax Cable

Signals are actually transmitted simultaneously on both the copper core and the copper shield. This is done so that both of these conductors generate their individual electromagnetic fields. These two electromagnetic fields eventually cancel out each other.

Once that happens, the cables can now be placed next to other sensitive electrical devices or even metallic objects, and there won’t be any worries about the cables acting like magnets and interfering with the signal in the copper core. 

Besides that, the fact that these electromagnetic fields cancel out each other means that external magnetic fields will also be prevented to some extent.

Specifications For Design of A Coaxial Cable

Even if you have the four basic elements that make up a regular coax cable, it would be difficult to control other factors like attenuation, frequency, and the power handling capability of the cable.

The construction of coax cables goes beyond the four components that it is made of. Factors such as the physical size of the cable, the outside diameter of the inner copper conductor, and the dielectric constant play an important role in the functioning of the coax cable.

Choice of impedance is also crucial when it comes to design since it directly influences the attenuation. Bell Laboratories conducted experiments in 1929 and found out that the best coaxial cable impedances suited for high-voltage applications were 30Ω, 60Ω, and 77Ω.

Coaxial cables with air as the dielectric resulted in an impedance of averagely 77Ω. However, when more effective dielectrics such as solid polyethylene or polyethylene foam are used, the impedance drops to 52-64Ω.

Today’s coax cables can operate at frequencies of up to 2.4GHz, and that makes it worthwhile for use in Radio and TV industries. They were once used for implementing computer networks, especially in the bus topology, but twisted pair cables have replaced them.

All in all, coax cables earn their popularity based on the fact that they are good at transmitting signals at a considerably high frequency with minimal interference.

About the Author 

Michael Alvarez has been working in the electronics and technology field for over 20 years. He enjoys sharing his experence with coaxial cable with others; while continuing to grow his knowledge.