What is the difference between Continuous and Discontinuous Shielding?
Have you ever wondered what the difference is between a continuous and discontinuous cable? You are not alone! It’s the question on EVERYONE’s mind…Rob, C2G’s technical marketing specialist, easily answered this question! Here is what he had to say.
What is a Shielded Cable
The first thing you need to know is that a shielded cable can be continuous or discontinuous. The only difference is the amount of protection the cable provides from EMI or RFI interference. Electromagnetic and Radio frequency interference (EMI/RFI) is all around us. Think of EMI/RFI as the static you might hear while talking on the phone. If the static on your phone becomes too loud, you often cannot tell what the other person is trying to say to you. When the noise becomes even stronger, the call might disconnect. The same parallel can be drawn when talking about shielded cabling. Using a shielded cable can help prevent EMI/RFI interruption in your signal and eventual damage to your equipment.
Because EMI and RFI can cause equipment failure, shielded cables are becoming increasingly necessary in many network installations. However, selecting the correct type of shielded cable for your application can be confusing. Let’s discuss the advantages of continuous and discontinuous shielded cables.
Shielding that contains a screen, sheath, or cover that substantially reduces the coupling of electric, magnetic, or electromagnetic fields into or out of circuits or transmission lines. Shielded cables should be grounded at both ends of the cable for best performance.
This is the classic version of a shielded cable. It provides the most protection from EMI and RFI interference. However, this additional protection also comes with several key disadvantages. The first is weight. A shielded Ethernet cable weighs on average about 12% more than an unshielded cable. That doesn't mean much when you have a single 4oz cable. But if your building has dozens or maybe hundreds of individual shielded cables the combined weight could damage the physical infrastructure
The second disadvantage is flexibility. Because the cable is surrounded by a continuous shield it prohibits flexibility of the cable. In permanent installs, this isn't so much of an issue, though you must be careful when pulling the cable through conduit. But in applications where the cable is attached to something that’s moving, like a robotic arm, a swiveling camera, or tools used in manufacturing, the shield can be a problem. The shield inside the cable can break and grind against the insulation of the individual wires, eventually causing it to short out.
Shielding that contains separated, discontinuous metallic shield segments dispersed along a length of the cable to reduce both electromagnetic signals that emanate from the cable core and the potentially interfering electromagnetic signals that are generated by other sources. The metallic shielding elements are designed to be discontinuous to dismiss the need for grounding, which is a requirement for shielded cable designs and to allow for a smaller bend radius.
Think of the discontinuous shielding like a telephone cord or the spiral rings of a notebook. This shielding approach is to reduce both electromagnetic signals that emanate from the cable core and the potentially interfering electromagnetic signals that are generated by other sources. The metallic shielding elements are designed to be discontinuous to avoid any need for grounding, which is a requirement for shielded cable designs.
Discontinuous shielding provides more than sufficient immunity to external RF interference, even in environments where extremely high powered RF transmitters are in close proximity. This type of shielding is perfect for HD A/V applications from HDBaseT extenders
Some other advantages of discontinuous shielding is that it allows for higher cable density and performance without grounding or bonding. It also has a smaller bend radius, which can be helpful for tighter installs, through conduit.