LMR400 Coax: A Brief History

LLMR coax cable was created as a more modern equivalent to the older RG-series cables. Each type of LMR coax is made to replace a certain kind of RG-series cable with LMR400 coax specifically designed to replace RG8. Each RG-series cable has a number that was simply used for military designation when the cable was originally created. RG-series coax got its start by being used by the US military for radio communications during WWII. RG8 (and by extension LMR400 coax) is still used for radios today, typically by amateur radio enthusiasts. RG8 can also be called RG8/U (Universal). Additionally, there is another version called RG8X, which is made from thinner cable to increase flexibility but maintains the same signal strength as a thicker cable. After WWII ended and radios started to become more widespread throughout America, coax cables became increasingly widespread alongside them.

As television and other new communications technologies were developed, they too began to use coax cable. The coax did not need to be changed to adapt to these new electronics, so pre-existing infrastructure could be used even as new devices were invented. But in recent years, RG-series cables have begun to reach their limit. With that in mind, the coax cable industry decided that it was time for an upgrade. LMR coax was the result of this project, a new breed of coax engineered to keep up with modern applications.

New LMR400 Coax Improves Upon Old RG8 Coax

There are different cable options for both RG-series and LMR coax. Most of the LMR cables were created to replace a specific RG cable. LMR400 coax is meant to replace RG8. While there are different versions of RG8 (such as RG8U and RG8X), LMR400 coax was made to surpass them all. The main draw of LMR coax is better resistance to attenuation (signal loss). Coax cables are made in layers; going from the outside in there is the jacket, shielding, dielectric, and conductor. Conductors are the central piece at the core of the cable; the metal that actually carries electrical signals down the length of the cable. Every other layer acts as insulation. This works to keep the coax signal contained while also keeping signal interference out. Other cables and machinery that use electricity can generate electromagnetic interference (EMI) and create signal loss. The dielectric, shielding, and jacket protect the conductor from that while also providing the cable with increased physical durability.

At short-range distances it can be difficult to see any different between LMR400 coax and RG8 since they are meant to be used as long-range cables. As they become longer, the difference in signal quality can be observed even without measuring equipment. As cables become longer, it becomes harder to maintain a strong signal. Working better shielding into the cable was one of the main purposes of inventing a new type of coax cable. As technology has advanced and more electric devices have been added to everyday life, EMI has become stronger and makes it more difficult for cables to function in the modern world compared to previous decades.

LMR400 Coax: A Versatile Cable for Any Situation

LMR400 coax is slightly on the thicker side for coax cables, with a 0.405” diameter. Thicker cables are less flexible but can transmit stronger signals. This makes LMR400 coax ideal for longer cable runs, such as running cables through a bigger building like a school or hospital. Coax cables like these commonly run through walls, ceilings, and floors to connect TVs and Internet modems in modern settings.

Even with LMR coax available, RG-series coax does still see use today. The reason for this is that RG-series cable costs less. When budgeting, those lower costs can seem good at a glance. However, always remember that you get what you pay for. RG8 cable is an old technology, meaning it sends weaker signals, is more vulnerable to EMI and other signal loss, and has less durability since it is made from more fragile materials. Even disregarding the performance issues, these weaker materials make RG8 wear out quicker, lowering the lifespan of the cable. A little money can be saved in the short run, but RG8 cable will never run as well as LMR400 coax.

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Danish Mehmood
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