Allied Encyclopedia: Low Loss Coaxial Cable

What is low loss coaxial cable?

Have you ever heard the term “low loss coax” and wondered what makes it different from standard coax cable? You probably aren’t alone.

Low loss coax cable gets its name from its low attenuation over distance. Attenuation is expressed in decibel per foot and is explained as a gradual loss in intensity through a medium, like the loss of a signal along the length of a cable. Minimizing the amount of loss in a cable run will increase the performance of the cable.

So, what is low loss coax? It’s coaxial cable that has less signal loss during transmission.

How does low loss coaxial cable reduce signal loss?

The amount of signal loss a cable experiences is dependent on several factors, such as frequency, cable length, cable diameter, and the electrical properties of the chosen dielectric, conductor, and shielding methods.

As the signal encounters resistance in the conductors and dielectric, some of the signal is converted to heat energy, which leaks out of the cable. Outside signals can also leak in; interference from outside signals may create noise and disruptions. The longer the cable and the higher the frequency, the more signal loss these variables cause.

There are multiple ways to combat high attenuation.

One way is to use a larger cable, because the chance of signal loss caused by conductor resistance decreases with an increase of the cable’s diameter, so a larger cable means lower loss.

Some applications may warrant a conductor with superior electrical properties. Although more expensive, a silver-plated copper conductor will achieve lower loss levels than the commonly used bare or tinned copper.

The dielectric of the cable is also important to the attenuation of the cable. Look for PTFE over PE, and consider putting more air into the dielectric, like Expanded PTFE. Cables with foam polyethylene dielectrics have about 15-40% lower signal loss than solid polyethylene of the same size. Low loss cables like LMR 195 and LMR 400, manufactured by Times Microwave Systems, are made with a foam polyethylene (FPE) dielectric.

LMR Low Loss Coaxial Cable

LMR Low Loss Coax Cable

So, what’s the difference between Low Loss Coax and RG Coax?

The key difference is in the shielding. Low loss coaxial cable employs multi-layer shielding that blocks radio frequency (RF) more efficiently than standard RG coax. High performance low loss coaxial cables such as LMR 240, LMR 600, and LMR 900 cables feature a multi-laminar aluminum composite tape which is bonded to the dielectric, providing 100% coverage as well as a second moisture barrier. A tinned copper outer braid supplies a positive ground and means for connector attachment. The RF shielding on these LMR cables boasts more than 90dB of isolation shielding—that’s 50 dB greater than typical single shielded coax.

In addition to the shielding, low loss cable can also have different conductors from what is used in RG coaxial cable. The conductor inside of low loss cable is typically solid, whereas the conductors in RG can be stranded, and stranding can cause higher attenuation.

By having considerably more effective shielding and utilizing a single, solid conductor, low loss coax prevents more signal leakage and attenuation than an RG coax cable.  

This makes low loss cable ideal for use in any high performance coaxial cable application. It’s a common choice for rooftop installations, in-building runs, tower and pole feeder runs, and jumper assemblies in wireless communications systems. Though there are many applications for this cable, low loss cable excels in wireless applications because of the decreased chance of losing a signal. For superior performance, look for cables that are highly flexible, non-kinking, and have easily installable connectors because these characteristics reduce the potential for signal loss.

View full low loss coax cable specs to learn more or call your sales rep at 800-472-4655 with any questions.

About awcwire
Allied Wire & Cable is a value-added manufacturer and distributor of electrical wire and cable, tubing, and more. We are a family owned and operated company, serving a wide range of industries, including the military, automotive, aerospace, and telecommunications markets. Allied is headquartered in Collegeville, PA. Additional locations can be found across the US, in Merrimack, NH, Tampa, FL, Pewaukee, WI, and Las Vegas, NV. For more information on Allied, visit our main website at www.awcwire.com.

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