LMR240 usually has lower attenuation than RG58, especially when the cable length increases or the working frequency moves into UHF, cellular, WiFi, or other higher frequency RF links. RG58 is still useful for short 50 ohm RF jumper cables, test leads, and equipment wiring where the total cable loss stays within the system margin. The better choice depends on frequency, length, total loss budget, and how much signal the system can afford to lose through the cable assembly.
The Main Difference Is Signal Loss
LMR240 and RG58 are both common 50 ohm coaxial cable options, but they are not equal when lower attenuation is the main goal. LMR240 is built as a low loss coaxial cable, so it usually keeps more signal power over the same distance. RG58 is a standard coaxial cable that is easier to use in many short jumper applications, but its loss becomes more noticeable as frequency and length increase.
For a short cable inside a device, the difference may be small enough that RG58 still works well. For an antenna cable running several meters, the difference can become part of the link budget. That is where LMR240 starts to show its value.
Why LMR240 Has Lower Attenuation Than RG58
Attenuation is affected by conductor size, dielectric material, shielding structure, cable diameter, and operating frequency. LMR240 uses a larger overall cable size than RG58 and is designed for lower loss RF transmission. This gives it an advantage when the signal travels through a longer cable path.
RG58 is smaller and more flexible in many assemblies, but that convenience comes with higher cable loss. In short connections, the extra loss may not matter. In longer antenna feeders, wireless equipment links, or higher frequency connections, the added loss can reduce the signal level reaching the antenna or receiver.
Frequency Makes the Difference More Obvious
At lower frequencies, RG58 can still perform acceptably in many short cable assemblies. The loss exists, but it may not be large enough to affect the system. This is common in short equipment jumpers, low frequency test setups, and simple 50 ohm connections.
As frequency increases, attenuation rises. The same cable length that works at a lower frequency may create too much loss at 900 MHz, 1 GHz, 2.4 GHz, or higher bands. In these frequency ranges, LMR240 usually gives a clearer advantage because it reduces the amount of signal lost along the cable.
Cable Length Decides Whether the Upgrade Is Worth It
The attenuation difference between LMR240 and RG58 becomes more important as cable length increases. A short RG58 cable may add only a small amount of total loss, so changing to LMR240 may not bring a visible improvement. This is why RG58 is still used for many short RF jumper cables.
When the cable reaches several meters, the loss starts to accumulate. At that point, the difference between a standard coaxial cable and a low loss coaxial cable becomes easier to measure. If the link already has limited signal margin, the lower attenuation of LMR240 can help keep more power in the RF path.
For longer runs, the question is no longer simply whether LMR240 is better than RG58. The real question is whether the total insertion loss is still acceptable at the required frequency. If the cable becomes too long, even LMR240 may need to be compared with a larger low loss cable.
If cable length is the main concern, our guide on how to choose RF cable length to reduce signal loss explains how length changes the final loss in an RF path.
When RG58 Is Still Acceptable
RG58 is still a practical cable when the assembly is short and the loss requirement is not strict. It is often suitable for short RF jumper cables, test leads, equipment wiring, low frequency links, and cost sensitive 50 ohm cable assemblies.
For example, if the cable only connects two nearby ports inside an enclosure, the lower loss of LMR240 may not be necessary. The smaller size and easier handling of RG58 can be more useful in compact equipment, test benches, and temporary connections.
The limit appears when the cable length grows or the working frequency rises. RG58 can still transmit the signal, but it may use up more of the available link budget. If the system already needs every bit of signal margin, RG58 is no longer the safer choice.
When LMR240 Is the Better Choice
LMR240 is the better choice when lower attenuation is part of the project requirement. It is more suitable for medium length antenna cable assemblies, wireless equipment links, cellular gateway antenna cables, outdoor antenna jumpers, and RF paths where signal loss needs to be reduced.
If the cable connects a radio module to an external antenna, the loss in the cable directly reduces the signal delivered to the antenna. The same applies on the receive side, where cable loss can reduce the signal reaching the receiver. In these cases, LMR240 helps protect the link budget better than RG58.
LMR240 becomes a practical option when an existing RG58 cable is causing noticeable signal loss. If cable attenuation is already taking up too much of the link budget, replacing RG58 with LMR240 can often improve signal levels without requiring changes to the radio, antenna, or overall system design.
FAQ
Conclusion
LMR240 is usually better than RG58 when lower attenuation is the main requirement, especially at higher frequencies or longer cable lengths. RG58 still has value for short, flexible, and cost sensitive RF jumper cables where total loss remains acceptable. For a custom RF cable assembly, the final choice should be based on working frequency, cable length, total loss budget, connector interface, impedance, and required insertion loss.