Shielded Cable: What it is and Why You Need it!
Shielded cables are cables that are encased in a form of conductive layer. This layer is designed to shield the internal conductors from electromagnetic interference, or EMI. This shielding becomes increasingly important when the cable is being installed near other equipment that is likely to generate EMI, such as in a data center and can help protect the cable from electrical surges.
So what are the different types of cable shielding?
Well for Ethernet Cable you have a few options
- UTP – Unshielded twisted pair
- F/UTP – Foil Unshielded Twisted Pair
- U/FTP – Unshielded Foil Twisted Pair
- S/FTP – Shielded Foil Twisted pair
Starting with the lowest level of shielding, UTP, this cable provides no shielding from EMI. These cables are generally more cost efficient and easier to work with, at the cost of having no form of EMI resistance.
F/UTP, or Foil Unshielded twisted pair, has an internal layer of shielding that wraps around all of the twisted pairs. This shielding is just below the jacket and has a copper drain wire connected to it. This drain wire is grounds the electricity after the cable has been terminated, and is an essential part of all shielded cable. As seen below, there is only one layer of shielding that encases all of the conductors, however each individual twisted pair remains unshielded.
For a guide on how to terminate this cable, check out our post on Terminating RJ45 Modular Plugs!
U/FTP, or Unshielded Foil Twisted Pair, has individual foil shielding wrapped around each of the twisted pairs and is essentially the opposite of F/UTP. As shown in our image below, each pair clearly has its own foil shielding. This form of shielding provides high levels of EMI resistance, and is generally more expensive than the types of shielding listed earlier. Due to the shielding being applied to each pair individually, terminating this cable can be difficult when compared to unshielded cable.
The highest level of shielding is S/FTP, or Shielded Foil Twisted Pair. As you can see below, this cable combines the shielding of both U/FTP and F/UTP. This cable features a foil shield that encases all of the conductors, as well as individual foil shielding for each twisted pair. Like all shielded cable, this cable also requires a drain wire to ground the electricity after termination. While terminating this cable can be a harder process than terminating unshielded cable, this cable provides the highest level of EMI protection to help ensure data quality.
For Coaxial cable, there is often a higher level of shielding required when compared to ethernet cable. In fact all coaxial cable requires some form of shielding.
So what are my options for Shielded Coaxial Cable?
- Braided Shielding
- Dual Shielding
- Quad Shielding
Braided shielding features either copper or aluminum wire tightly braided together. As picture below, this shielding is located beneath the jacket of the cable, and right above the dielectric. The purpose of this shield is not just to prevent EMI, but also to help keep the RF signal inside the cable. For Coaxial cable, the shielding helps to prevent signal degradation of large distances.
Dual shielding, features both a wire braided shield, and a solid aluminum shield. These two shields provide a higher level of shielding and help the RF signal travel further. As you can see in the cable image below, the braid of this shield is not woven as tightly as the one shown above. The cable above features a 95% braided shield, while the dual shielded cable features a 60% shield. This is because the 100% foil shield below the braid provides a high level of shielding already, so a tightly woven braided shield is not necessary.
Quad shielding takes a wire braided shield and solid aluminum shield and doubles it. Once again you can see below, that the braid of this shield is not woven as tightly as the braided shield in the first coaxial cable. In fact, the first braid of this shield is a 60% shield, and the second is only a 40% braid. Still, this level of shielding is dramatically higher than that of the cables before it, as the two layers of 100% foil shielding make up the difference.