Choosing a low loss cable is not just about picking RG or LMR. In real RF cable assembly projects, the result depends on several practical factors, such as working frequency, cable length, impedance, connector type, available routing space, assembly method, and test requirements. RG cable is often used for short jumpers or compact devices where space is limited. For longer antenna feeders or higher frequency applications, LMR or similar low attenuation coaxial cable is usually a more suitable option.
What Low Loss Means in a Cable Assembly
Low loss describes how much signal power is lost as the signal travels through the coaxial cable and the finished assembly. The loss is usually shown as insertion loss, and it changes with frequency and length. A short cable at 900 MHz may pass a signal with limited loss. The same cable at 5 GHz, or at a much longer length, may create a very different result.
For a finished RF cable assembly, cable loss is only part of the answer. The connector interface, cable termination, bend near the connector, shielding structure, and test method can all change the measured result. A buyer comparing low loss cable options usually needs the finished length, connector series, impedance, target frequency, and expected test items before the cable option can be confirmed.
RG Cable Options for Short and Moderate RF Runs
RG cable covers many coaxial cable types. The name alone does not tell the full performance. RG174 and RG316 are common in small RF jumpers, compact devices, GPS antenna cables, wireless modules, and places where the cable has to pass through a tight route. Their smaller diameter makes routing easier, while the length and frequency need to stay within a reasonable range for the link budget.
RG58 is often seen in general 50 ohm RF jumpers and equipment connections. It gives more mechanical size than very small coax and can work in many moderate length assemblies. For projects that need higher temperature resistance, stronger shielding, or a more stable jacket material, cable types such as RG400 may enter the discussion. The final choice still depends on the connector, length, routing space, and frequency.
RG cable works well in practical cases where the assembly is short, the device port is small, or the cable needs to pass through tight spaces with multiple bends. However, as the cable length increases, the operating frequency rises, or the system has stricter insertion loss limits, RG cable may no longer meet the performance requirements.
LMR and Equivalent Low Attenuation Cable Options
LMR type cable and equivalent low attenuation coaxial cable are often considered when a standard RG cable creates too much loss for the target length or frequency. Common project discussions may include LMR195, LMR240, LMR400, LMR600, or equivalent cable structures. These cables are often selected for antenna feeders, outdoor wireless equipment, cabinet to antenna jumpers, communication antennas, and longer 50 ohm RF links.
For a broader cable selection guide, you can also read our article on how to choose a low loss coaxial cable.
The advantage is lower attenuation for the same signal path. The tradeoff is mechanical size. A thicker low attenuation cable can make the assembly harder to route inside a cabinet, vehicle, enclosure, or compact antenna housing. The connector may also become larger, and the tail section may need more clearance.
Compare Cable Loss at the Working Frequency
Cable loss becomes more serious as the frequency and cable length increase. In short internal RF jumpers, RG174, RG316, or RG58 may be enough when the cable route is compact and the allowed insertion loss is not strict. For longer antenna feeders, outdoor wireless equipment, cabinet to antenna jumpers, or higher frequency links, LMR195, LMR240, LMR400, or equivalent low attenuation coaxial cable is usually a stronger starting point.
For GNSS antenna cables around the GNSS band, small RG cable is often used when the cable is short and the device space is limited. If the GNSS cable becomes longer, or the receiver side has a tighter signal budget, a lower attenuation cable should be checked before confirming the assembly. For WiFi, LTE, 5G, and wireless gateway cables, the cable option should be reviewed at the project frequency, because a cable that works acceptably at a lower band can lose too much signal at 2.4 GHz, 5 GHz, or a higher project frequency.
A practical selection path is simple: use RG cable for short, flexible, space limited assemblies; use LMR or equivalent low attenuation coaxial cable when frequency and length start to increase loss; use a custom RF cable assembly when the project needs a fixed connector type, finished length, cable route, label, jacket, and S21 insertion loss result.
To estimate cable body attenuation by frequency and length, you can also check our coaxial cable loss chart guide.
Cable Diameter, Flexibility, and Routing Space
Lower loss often comes with a larger diameter, more shielding, or a different dielectric structure. That can improve attenuation, while it also changes how the cable fits into the product. A cable that works well on a bench may feel too stiff when it enters a narrow enclosure, passes near a PCB, or connects to a right angle port.
Routing space affects the cable option. A small module may need RG174, RG316, or another flexible cable because the path is short and the bend is tight. A cabinet antenna feeder may accept LMR240 or LMR400 because the route is longer and the enclosure has more space. Outdoor equipment may need attention to jacket material, UV exposure, moisture protection, and connector sealing.
When a Custom RF Cable Assembly Makes More Sense
A custom RF cable assembly makes sense when the ports, length, routing, and performance are already clear. Instead of picking a bulk cable first and figuring out the rest later, it’s easier to treat the cable, connectors, length, labels, jacket, orientation, and testing as one complete assembly.
Sample confirmation is usually the easiest point to check these details. With a sample in hand, you can see whether the connectors fit properly, whether the length is right, how the cable bends near the device, how the route works, and what the actual insertion loss looks like. If the project later goes into mass production, the same drawing, cable type, connector, and test items can be kept to maintain consistency.
Custom assemblies are especially useful for antenna feeders, GNSS cable assemblies, wireless gateway cables, N Type outdoor jumpers, SMA test cables, FAKRA cable assemblies, and mixed interface cables. These projects often involve more than one requirement, so the assembly drawing and test plan become part of the cable decision.
Before sending an RFQ, you can use our RF cable assembly specification checklist to prepare the required details.
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Conclusion
Low loss cable selection is clearer when viewed as part of a finished RF cable assembly. RG cable suits short jumpers, compact devices, and general links. LMR or similar low attenuation coaxial cable is better for longer antenna feeders and higher frequency paths where insertion loss is harder to control. The final choice should consider working frequency, cable length, impedance, connector type, routing space, and test data together. If your project involves special length, right angle connector, outdoor jacket, mixed interface, or low loss requirements, you can share drawings, samples, or RFQ details with the Bafitop team for review.