In RF engineering, every inch of cable introduces insertion loss (attenuation). The higher your frequency (like 2.4GHz or 5G) and the longer your cable run, the more your signal turns into wasted heat. If you are dealing with weak signals, you need a low-loss RF cable.
Let's skip the marketing fluff and look at what actually makes a cable "low loss" and which exact models you should be sourcing for your hardware projects.
What Makes a Cable "Low Loss"?
Not all coaxial cables are created equal. The performance of a low-loss cable comes down to its internal construction:
Foam Dielectric: Standard cables use solid plastic (PE) insulation. Premium low-loss cables use Foam PE. The injected air lowers the dielectric constant, which dramatically reduces signal loss.
Double Shielding: Cheap cables use a single copper braid. Low-loss cables feature an inner aluminum foil layer (for high-frequency protection) wrapped in a tinned copper braid (for low-frequency protection and durability).
Solid Center Conductor: While stranded cores are more flexible, a solid copper core offers significantly better RF conductivity and lower resistance.
The Best Low Loss Cables: The LMR Series
When hardware engineers need to minimize attenuation, they rely on the LMR series (or high-quality equivalent alternatives). Here is the breakdown of the best options based on your application:
1. LMR-100: Best for Internal Routing
If you need to connect a PCB module to an external antenna port inside a tight enclosure (like an IoT gateway or drone), LMR-100 is your best choice.
Diameter:~2.79 mm (0.110 inches)
Why use it:It is highly flexible and serves as a direct, lower-loss replacement for legacy RG-174 and RG-316 cables. It is the standard for U.FL to SMA pigtails.
2. LMR-240: The Perfect "Sweet Spot"
LMR-100 has too much loss for long runs, and LMR-400 is too thick to bend easily. LMR-240 is the ideal middle ground.
Diameter:~6.10 mm (0.240 inches)
Why use it:It offers excellent flexibility while maintaining low attenuation at Cellular and Wi-Fi frequencies for runs up to 20 or 30 feet. It is heavily used in vehicle mounts and outdoor NEMA enclosures.
3. LMR-400: Best for Long Outdoor Runs
If you are running a cable up a 50-foot tower for a WISP base station or a commercial Wi-Fi access point, LMR-400 is the industry standard.
Diameter:~10.29 mm (0.405 inches)
Why use it:It is thick and stiff, but its attenuation characteristics are phenomenal. For long outdoor runs, LMR-400 ensures the signal actually makes it from the radio to the antenna.
Stop Using RG-58 for High Frequencies
Many older guides still recommend RG-58 for general RF use. While RG-58 was fine for 27 MHz CB radios in the past, it is a terrible choice for modern IoT systems.
At 2.4 GHz, a 100-foot run of standard RG-58 will lose over 20 dB of signal (meaning 99% of your transmit power is lost in the cable). By swapping that exact run to LMR-400, your loss drops to just 6.8 dB. If your system operates above 400 MHz, drop the RG series and upgrade to LMR equivalents.
Do Not Compromise on Connectors
A premium low-loss cable is useless if the connectors are poorly installed. Always specify high-quality SMA, N-Type, or TNC connectors made of brass with gold-plated center pins. Factory-crimped or soldered cable assemblies will always outperform DIY field terminations by preventing VSWR spikes.
Need Custom Low-Loss Cable Assemblies? We manufacture custom RF cable assemblies using premium low-loss coax and strictly tested connectors. Tell us your frequency, required length, and connector types, and our engineers will provide a quote. [Contact Us for Custom Cables]