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Making Sense of RG | What do the Numbers Mean?

Thursday, July 18, 2019

RG, or Radio Guide, was the original military specification for coax cable dating back to World War II and is now referred to by the Mil-C-17 standard. The numbers following RG in a part number are generally just an indicator of size, referring to the diameter of the cable with higher RG numbers having a thinner central conductor. Most RG numbers refer to specific diameters of cables but also shielding type, jacket type, and dielectric type (which gives its impedance property). Different types of RG ratings for each type of coax cable help to distinguish the distinct characteristics and specifications of the cable. For example, in the designation RG#/U, the U indicates general utility use.

Generalizations are difficult to make about different types of RG cables since the numbers in the designation are somewhat arbitrary and are not always indicative of the specific form and function of the cable itself. Therefore, when looking for a coax cable, the most important thing to know is the frequency you are looking to send through the cable. After you have narrowed down your options to fulfill that requirement, you then want to look in more detail at the cable specifications to find exactly what you need. This is especially true when looking at different manufacturers because many of the standards have become vague, meaning that RG58B/U could have very different characteristics from one manufacturer when compared to another.

The two main types of coax cables are ones with an impedance of 75 Ohm and ones with an impedance of 50 Ohm. In these cables, Ohm refers to the impedance, which is the measure of resistance in the cable to the flow of electrical energy. Cables with 50 Ohm ratings are used for data and wireless communications while 75 Ohm cables are used for video signals. 

Each RG cable type offers a variety of capabilities and ideal uses in consumer applications, below are some of the most common options:

  • RG6 cable is the industry standard for cable and satellite signal transmission. It’s larger conductors provide better signal quality and the thicker dielectric insulation, made with a different kind of shielding, allows more effective handling of GHz level signals. RG6 is a thin cable that can be coiled or bent for residential installations within the ceiling or wall. Applications of RG6 cable include television, internet, and video.

  • RG11 cable is a thick, inflexible cable used in outside and underground applications to minimize the signal loss in long runs. More difficult to work with. Higher gauge than others, providing more space for signals to transfer. High-definition television is the most common application of RG11 cable.

  • RG59 cable is a very popular cable in domestic and residential settings. It is similar to RG6 but has an even thinner center conductor. RG59 is ideal for short runs and low-frequency transmissions within the home. Otherwise inferior to RG6 in other applications. Ideal for CCTV systems applications.

Low loss coax cables are similar to RG coax cables in many aspects but the main difference between standard RG coax cable and low loss coaxial cable is the shielding. Low loss cable has far better shielding than RG style cable thus making it better able to achieve low loss characteristics. Low loss cables also use a solid center conductor which offer lower attenuation than the stranded conductors that are typically found in RG cables. Applications for low loss cables typically include WLAN, cellular, PCS, ISM and many other wireless applications.

In many situations, the low-loss cable is particularly important and is often used extensively in wireless system installations for any antenna-to-radio setup. Often referred to by its series number, such as 200-series cable, the number is typically a rough approximation of the diameter of the cable. The higher the number, the thicker and heavier the cable, and lower attenuation over the entire length. With this, higher series numbers are used in cases where the antenna is permanently installed at some distance from the radio while lower series numbers are used in cases where the antenna is closer, especially in portable setups and where the weight of the cable is important. 

If you are looking for coax cable, Allied Wire & Cable can advise and supply you with a variety of RG and Low-Loss cable options.

Filed Under: Allied Encyclopedia

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