Before explaining the differences between these two types of construction of Coax cables, we need to understand how this type of cables are constructed.
The Coax cable, or coaxial cable, has a center conductor and wrapped around this center conductor it as a hard foam insulation known as dielectric. Wrapped around the dielectric comes what we call shielding of the cable, in this case Dual Shield and Quad Shield that we are going to talk below and at the end it has a sheath called jacket made by different types of plastic depending on the application.
What is a dual shield coaxial cable?
The designation of a Dual Shield coaxial cable means that it has two shields against environmental issues like electromagnetic interferences. It has one tape shielding and two wire braid shields.
Regarding the construction it is one foil tape wrapped around the dielectric and one wire braid.
What is a quad shield coaxial cable?
The designation of a Quad Shield coaxial cable it means that it has four shields against environmental issues like electromagnetic interferences.
It has two foils tape shielding and two wire braid shields.
Regarding the construction it is one foil tape wrapped around the dielectric, one wire braid shield, warped around the wire braid it has another foil tape and then another wire braid shield.
The Quad shield coax cable has a better protection/shield against environmental issues comparing to the Dual Shield coaxial Cable.
What are the main differences between them?
The Dual shield has a foil tape shielding wrapped around the dielectric and a wire braid shield that can be aluminum wire braiding or cooper and the Quad Shield has two foils tape shielding and two wire braid shields.
Regarding the construction of the Quad Shield, it is one foil tape wrapped around the dielectric, one wire braid shield, warped around the wire braid it has another foil tape and then another wire braid shield.
The main difference between them is the grade of shielding that each cable has.
When is a dual shield cable needed?
The Dual Shield is mostly used on home installations where there is a lower possibility for environment issues. It has a higher attenuation (signal loss) but the distances that it will be used are small so there is no problem, and this type of construction allows a smaller bent radius comparing to the quad shield there for a better solution for home installations.
When is a quad shield cable needed?
The Quad shield cable is mostly used on business installation that has a bigger probability of environmental issues like electromagnetic interference and/or radio frequency interference. For example, when there is no efficient separation from the electrical installation to the coaxial installation therefor the best solution is to use the quad shield cable. The quad shield has also a lower attenuation (signal loss) comparing to the dual shield.
Keep in mind that both coaxial cables (Dual Shield and Quad Shield) have the same maximum run length. For that reason, please verify first the conditions and parameters that are needed for your installation and use the one that complies the best.