Coaxial Cable FAQ


What does AWG mean?  AWG means American Wire Gage, the […]

What does AWG mean?
 AWG means American Wire Gage, the standard measurement of wire size.
Why can't I use aluminum and copper together?
In some configurations, they can be used together. In others, they can not. It is common to see copper-clad aluminum, especially in broadband (CATV) and high-frequency coaxial center conductors where skin effect occurs. Those combinations are metallically bonded. If you combine aluminum and copper as loose wires, there is a voltage potential difference between them of 2 volts! All they need is time, or an acceleration medium (such as moisture in the air between them), and they will begin to eat at each other ("galvanic corrosion"). If you are using aluminum and copper to carry power, the two metals expand and contract differently when heated and cooled ("coefficient of expansion"). This means that a tight connection will begin to loosen itself over time as electricity passes through it. Eventually, the connection can be so loose, and the resistance so high, that the circuit might be unable to operate. At high voltage or high power, the cable could melt or the heat generated could start a fire.
What is attenuation?
As signals travel, they become weaker. This is as true with sounds traveling through air as it is with electrical signals traveling through wires. Attenuation is usually represented as a loss of decibels (dB). Other factors in the construction of cables make higher frequencies attenuate greater ("high frequency attenuation"). Cables, as listed in the Belden catalogs, intended for carrying signals, will show a list of frequencies and the loss at that frequency per standard length (100 ft. or 100 m) so that the performance of similar cables can be compared.
What is capacitance?
Capacitance is the ability to store a charge. In cables, especially in digital applications, capacitance is a bad thing. Higher capacitance reduces overall cable run length and degrades the original signal.
What is coax cable?
Coax is a cable in which one conductor is insulated with a dielectric material and then surrounded by the other conductor, usually referred to as the center conductor and shield. The shield is typically a serve, braid, or foil braid configuration. typical applications are video, RF, and microwave.
What is Dielectric?
A dielectric material is used as the insulation material in cable products. Typical dielectric materials are polyolefin (PE or PP) and Teflon. PVC is normally not referred to as a dielectric material
What is a foil shield?
A foil shield is an aluminum foil surrounding the components or core of a cable. It is used in several types of cables and is a lower cost effective means of shielding the cable from RF signals
What’s the difference between a braid and a French braid?
A Braid is a double serve with all 16 (or 24) carriers of conductors interweaved. The French Braid only has one set of carriers interweaved.
What is impedance? 
Impedance is the total opposition a cable offers to alternating current. It includes both resistance and reactance and is generally expressed in Ohms.
What is ink jet printing?
Ink jet printing is a method used to print on the jacket of various cables or components. The letters and numbers are 'shot' onto the cable in a dot-matrix format. Therefore the print quality is not as good as a print wheel but the legend ("writing") can be changed instantly. Some cable markings, such as consecutive footage numbers, can only be done by ink jet printing. Other things, such as logos or symbols, are difficult or impossible with ink jet printing.
What is Mil-Spec?
Mil-Spec is short for Military Specification, and refers to documents such as MIL-C-17G which detail test/measurement procedures and general cable design construction.
What is PVC?
PVC means polyvinyl chloride and is a common plastic used for insulating and jacketing many wire and cable products.
Performance of PVC
There are many formulations of PVC with different attributes, so the range of performance is equally great.
Color ability: excellent
Flexibility: good to excellent
Flex-life: Good to excellent
Flammability: poor to very good
Dielectric Constant: ~3 to 5
What is resistance?
Resistance in DC circuits is the opposition a cable offers to current, measured in ohms. In AC circuits, resistance is the real component of impedance.
What does RG mean?
RG refers to old Mil-Spec cable identifications such as RG-8/U. "RG" means radio guide. These ratings are only used as reference today since RG is no longer used in the Mil-Specs. RG-8A/U is now M17/163-00001.
RG Type
An RG Type cable is one that is manufactured similar to, but not exactly the same as, the Mil-Spec specifications.
RG-U Defined
RG means Radio Guide. U means Universal.
What is a shield?
A shield is a metal construction of either aluminum foil, aluminum conductors, or copper conductors surrounding the interior of a cable. The shield helps prevent interference or noise from entering the cable and also helps prevent signals from leaving the cable and interfering with adjacent cables.
What is SRL?
SRL stands for Structural Return loss. It is a measurement of the manufacturing consistency and quality of the cable.
What is UL?
Underwriters Laboratory is a standards verification testing agency.
What is Velocity of Propagation?
Velocity of Propagation is the speed of an electronic signal traveling down a cable compared to the speed of light in a vacuum (which is defined as 100%). Changing plastics around wire, or foaming them to contain more air, will affect Velocity of Propagation. This has a significant effect on high frequency attenuation.