|Volume 10, Number 28|
Tips on Selecting the Right Coaxial Cable
|L-com's extensive line of bulk coaxial cable includes our RG58, RG59, RG174, RG179, as well as high-performance, low loss 100, 195, 200, 240, 400, 600, and 900 series. We stock both 50 Ohm and 75 Ohm bulk coaxial cable for all your video, wireless, and data networking needs, and can also custom manufacture coax bulk cable to your specifications.|
Selecting the right coaxial cable can go a long way toward satisfying the needs of a specific application. Which criteria are most important to the specifying process? Here’s what our customers need to consider when choosing coaxial cables:
There are basically two types of coaxial cables: those with an impedance of 75 Ohms (Ω), used mostly for video applications, and those with an impedance of 50 Ω, used mostly for data and wireless communications.
Typical 75 Ω cables are our RG59/U and RG6/U, which have a 22 AWG stranded center conductor to allow for cable flexibility. The common size cable can be easily terminated and is available in 100-, 500- and 1000-foot reels.
Typical RG-style 50 Ω cables for data are our RG174/U, RG188/U and RG316/U. These bulk cables can be used in applications where cable assemblies must be built in the field. Available in 100-, 500- and 1000-foot rolls, their stranded 26 AWG center conductors result in very flexible cables for tight-fit applications. Additionally, the bulk RG188A/U cable has a Teflon-taped outer jacket to help achieve a 200-degree C operating temperature, and the RG316/U has an extruded FEP outer jacket that helps achieve a 200-degree C operating temperature.
50 Ω cables are also available in the low-loss version 100-, 200-, and 400-series specifically for wireless applications.
Another important consideration is the operating frequency of the signal carried on the cable. As the frequency increases, the signal energy moves away from the cable’s center conductor to the cable’s shield outside of the conductor, a phenomenon known as the “skin effect”.
This has a direct correlation to how far the signal can travel over a cable of a certain length, for a given signal frequency and power level. The higher the signal frequency, the shorter the distance traveled.
See our Coaxial Cabling Tutorial here.
For example, an RG59/U cable with a 14 AWG center conductor can carry a signal (at a specific frequency and power level) about twice the distance as that of an RG11/U cable with a 20 AWG center conductor. In specifying a coaxial cable, it’s imperative to know how much cable attenuation is acceptable in a particular application.
|Cable attenuation is the amount of signal loss over a specific distance. In general, the higher the frequency, the larger the attenuation will be, and the larger the diameter of a cable’s center conductor, the lower the attenuation is. |
A coaxial cable’s characteristic impedance is an important parameter that affects the performance of the signal being carried over the cable. Also known as transmission impedance, it is defined as the relationship between a cable’s capacitance per unit length to its inductance per unit length. For optimum signal transfer, the cable’s characteristic impedance should be matched to the impedance/resistance of the load.