Coaxial cable uses a center wire, wrapped with insulation, which is then surrounded by a grounded shield with a braided wire strand, all to minimize the interference from other electrical and radio signals. Coaxial cable was originally used to transmit analog signals, but made the transition to digital signals deftly. There are two types of coaxial cable: copper and aluminum. Both use a corrugated outer structure to protect the cable and allow it to bend around corners.
Copper coaxial cables are more expensive than aluminum coaxial cables, by about a 40- to 120-percent margin depending on the diameter of the cable and how heavily shielded it is. Combined with rising costs of copper worldwide and a steady supply of aluminum, this price disparity is likely to rise. In wiring jobs where materials cost is a major concern, aluminum is the better choice.
Aluminum coaxial cable is typically half the weight of the equivalent copper coaxial cable. Both cable types list the outer diameter of the cable, rather than the diameter of the conductive lead inside the cable. Because copper is a better conductor, the inner lead is usually a tiny bit smaller, but the dimensions for inner leads are typically set by the ports they connect to. At the same outer diameter, aluminum cable is more flexible. This makes aluminum cables easier to bend around tight corners or the preferred choice where total transmission system mass is a consideration, such as running suspended cables between antenna towers.
Aluminum coaxial cable is less crush resistant than copper coaxial cable. Copper cable deforms at 175 pounds per inch of flat plate crushing force, while aluminum cable deforms at 75 pounds of pressure; this makes copper better suited to runs where the cables might be stepped on or run over in the course of routine operation. Copper cable also has a higher tensile strength -- the amount of force needed to stretch the cable to its breaking point -- with a rating of 750 pounds for copper cable, compared to 350 pounds for aluminum cable.
Electrical and Frequency Differences
Both cable types are built to the same standard when it comes to signal strength and impedance. For most commonly used cables, this is 75, 50 or 125 ohms, although there is considerable variation. Both cables are rated to switching frequencies up to 2,700 MHz, although copper's higher conductivity means that signals transmitted over it will have less noise or static. Signal noise becomes significant when static on the line degrades image quality or is read as erroneous signals in control systems or scientific instrumentation. In most cases, the difference in signal quality isn't noticeable. In situations where signal quality is critical, copper has a slight advantage.
- Hemera Technologies/PhotoObjects.net/Getty Images