Understanding LMR400 Loss: What You Need to Know

If you’re looking for a high-quality coaxial cable, you might have heard about LMR400. It’s a popular choice for a variety of applications, including Wi-Fi and cellular networks, amateur radio, and more. But one of the most important considerations when selecting a coaxial cable is the loss, or attenuation, that occurs as the signal travels through the cable. In this post, we’ll discuss LMR400 loss and what you need to know to make an informed decision.

What is LMR400?

LMR400 is a type of coaxial cable that has a solid copper center conductor, foam polyethylene insulation, and dual shielding consisting of a bonded aluminum foil and a tinned copper braid. The cable has a diameter of 0.405 inches (10.3 mm) and a 50-ohm impedance, which is the standard impedance for most RF applications. LMR400 is designed for low-loss applications and has a nominal attenuation of 6.6 dB per 100 feet (30 m) at 900 MHz.

LMR400 Loss: How Much Attenuation Occurs?

As mentioned earlier, loss is one of the most important considerations when selecting a coaxial cable. It’s the amount of signal that’s lost as it travels through the cable due to various factors such as resistance, dielectric losses, and radiation. In the case of LMR400, the loss is relatively low compared to other types of coaxial cables. Here’s a table of comparison for LMR400 loss at different frequencies:

Frequency (MHz)	Attenuation per 100 ft (dB)
10	0.4
50	1.1
100	1.6
400	3.9
900	6.6
1000	7.1
1500	9.3
2000	11.1
5800	24.4

As you can see, the attenuation increases as the frequency increases. This is due to the skin effect, which causes the signal to travel mainly on the surface of the conductor at higher frequencies, increasing the resistance and thus the loss.

Factors Affecting LMR400 Loss

The attenuation of LMR400 depends on several factors, including the length of the cable, the frequency of the signal, the temperature, and the installation method. For example, if the cable is kinked or bent too sharply, it can cause extra loss due to increased resistance. Likewise, if the cable is installed in an area with high temperatures, it can cause the insulation to break down, increasing the loss.

Conclusion

LMR400 is a popular coaxial cable for a variety of applications due to its low loss, high performance, and durability. When selecting a coaxial cable, it’s important to consider the attenuation or loss that occurs as the signal travels through the cable. The loss of LMR400 is relatively low compared to other types of coaxial cables, making it a great choice for long-distance and high-frequency applications. However, it’s also important to consider factors that can affect the loss, such as cable length, frequency, temperature, and installation method, to ensure optimal performance.

We hope this post has helped you understand LMR400 loss and what you need to know to make an informed decision. If you have any questions or comments, feel free to leave them below.