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Coaxial Cabling Terms


Attenuation (Insertion Loss): Loss of power. Attenuation is usually measured in dB loss per length of cable (ex. 31.0 dB/100Ft.). Attenuation increases as frequency increases.

Bend Radius: The amount of radius a cable can bend without any adverse effects.

Center Conductor: The solid or stranded wire in the middle of the coaxial cable.

Coaxial Adapter: A device used to change one connector type to another or one gender to another (ex. BNC to SMA Adapter).

Coaxial Cable: A two conductor cylindrical transmission line typically comprised of a center conductor, an insulating dielectric material and an outer conductor (shielding). Coaxial cable can be flexible, semi-rigid or rigid in nature.

Coaxial Connector: The interconnection device found at each end of a coaxial cable assembly. There are many common types of coaxial connectors such as: BNC, SMA, SMB, Type F, etc.

Dielectric: The insulating material that separates the center conductor and shielding.

Electromagnetic Interference (EMI): Electrical or electromagnetic energy that disrupts electrical signals.

Frequency: Number of times a periodic action occurs in one second. Measured in Hertz.

Impedance: The opposition to the flow of alternating or varying current. Measured in Ohms. Two common impedance values are 50 Ohms used primarily for data and 75 Ohms used to transmit video signals.

Insertion Loss: A measurement of attenuation determined by the system output before and after the connection of a cable and/or device.

Jack: The female connector usually containing a center socket.

Microwave Frequencies: Microwave frequencies range from Ultra-High Frequency (UHF) .3-3 GHz, Super High Frequency (SHF) 3-30 GHz to Extremely High Frequency (EHF) 30-300 GHz.

MIL-C-17: MIL-C-17 is a specification document that has been used since the 1940s to standardize the physical and electrical characteristics of coaxial cables. There is no longer any control of RG specifications so cables may perform differently than the cables that adhere to MIL-C-17.

Plug: The male connector usually containing a center pin.

RF (Radio Frequency): A frequency band from 3 MHz to 300 GHz. Primarily used for transmission of radio and television signals.

RG/U: A designation that originated with a US Government specification. No longer in effect. Currently used as a general reference. (R=Radio Frequency, G=Guide, U=Universal Specification). Letters that appear before the /U characters (i.e. A, B or C) means a specification modification or revision. For instance, it is common in the CB industry to see the designation RG-58A/U. The original RG-58/U coaxial cable had a solid center conductor. The "A" modification replaced the solid center conductor with a more flexible stranded center conductor (that is highly recommended for use in mobile installations). Other designators often seen are: A = Modification to the Solid Core Material Specification, B = Modification to the Outer Jacket Specification, C = Modification of the Dielectric Insulator Specification. These designators are not precise and specifications may vary from one vendor to another.

Shielding: Conductive envelope made of wires or metal foil that covers the dielectric and the center conductor.

Twinaxial: An offshoot of coaxial cabling. Two center conductors with one dielectric and braided shielding.

Velocity of Propagation (VP): Usually expressed as a percentage, VP is the transmission speed of electrical energy in a determined length of cable compared to the speed of light.

VSWR (Voltage Standing Wave Ratio): The ratio of the maximum effective voltage to the minimum effective voltage measured along a RF transmission line. This value generally increases with frequency and higher values are not desirable.