LMR100 normally provides lower attenuation and a more complete shielding structure than RG174 while keeping a similar cable diameter. RG174 can still meet the requirements of short RF jumpers when the finished assembly already has sufficient loss margin. A replacement decision also needs to cover connector termination, routing conditions, cable length, and test results because similar outside diameters do not make the two cables identical.
LMR100 and RG174 at a Glance
LMR100 and RG174 are compact 50 ohm coaxial cables used in antenna leads, wireless modules, GPS devices, IoT equipment, and other installations where routing space is limited. Representative LMR100A and RG174 constructions both have a nominal outside diameter of about 0.110 inch, or 2.79 mm. This close size makes LMR100 a possible performance upgrade where a thicker cable cannot fit.
Their internal constructions are different. A typical LMR100A cable uses a solid center conductor, solid polyethylene dielectric, aluminum tape, and an overall tinned copper braid. A representative RG174 cable uses a stranded center conductor, solid polyethylene dielectric, and one tinned copper braid shield. These differences affect attenuation, shielding, bending behavior, and connector termination.
LMR100A refers to a defined cable construction, while RG174 is produced in several versions. Conductor material, braid coverage, jacket material, temperature range, and attenuation can vary between RG174 products.
How Much Attenuation Does LMR100 Save
At 900 MHz, a published LMR100A specification lists typical attenuation of 22.8 dB per 100 ft. One representative RG174 construction lists nominal attenuation of 31.0 dB per 100 ft at the same frequency. Converted to one meter, the cable losses are approximately 0.75 dB for LMR100A and 1.02 dB for that RG174 construction.
The difference is about 0.27 dB per meter at 900 MHz. A 0.5 meter cable saves about 0.13 dB, a 1 meter cable saves about 0.27 dB, and a 3 meter cable saves about 0.81 dB. The improvement is measurable, but a very short jumper may not gain enough margin to justify changing a validated assembly.
Why Their Shielding and Construction Are Different
LMR100A uses aluminum tape under an overall tinned copper braid. The foil layer provides continuous coverage around the dielectric, while the braid adds conductivity, mechanical support, and a connection surface for the connector body. A typical RG174 construction relies on one tinned copper braid as its outer conductor and shield.
Lower attenuation and stronger shielding are also separate performance areas. A cable can have good shield coverage while still losing more signal through conductor and dielectric losses. The required comparison may therefore include both insertion loss and shielding performance when the cable runs near power wiring, digital circuits, motors, or other noise sources.
Coverage percentage and shielding effectiveness in dB are also explained in our guide to RF cable shielding performance.
Why does the center conductor change the mechanical response? Standard LMR100A uses a solid center conductor, while many RG174 cables use a stranded conductor. This difference can affect repeated bending, contact attachment, strip dimensions, and the stability of the terminated center contact.
Can LMR100 Replace RG174 in the Same Cable Assembly
Some RF connector part numbers are specified for both RG174 and LMR100A. This confirms that common termination hardware is available for the two cable types. It does not mean that every connector currently used with RG174 will also accept LMR100.
The connector drawing needs to list the proposed cable type or compatible cable group. The review also covers center contact dimensions, ferrule inner diameter, dielectric support, cable preparation dimensions, crimp die, solder process, boot, heat shrink, and strain relief. A difference in the inner conductor or shield stack can affect the termination even when the jacket diameter is the same.
An existing RG174 assembly can be converted to LMR100 after the connector parts and assembly process have been confirmed. A sample run can then check contact retention, ferrule crimp, cable pull strength, continuity, insulation, insertion loss, and return loss or VSWR.
When RG174 Is Still Sufficient
RG174 remains suitable when the cable is short and the finished assembly already meets the required insertion loss, return loss, and VSWR limits. A 150 mm or 300 mm internal jumper may gain very little total loss margin from a cable change, especially at lower frequencies.
RG174 may also fit a routing condition that benefits from its particular stranded conductor and jacket construction. This does not confirm unlimited flex life, but it can still be a practical choice for certain compact or flexible installations when properly evaluated.
When LMR100 Is Worth the Upgrade
LMR100 is useful when the assembly needs lower attenuation without increasing the cable envelope beyond about 2.8 mm. It can recover part of the link margin in a longer antenna lead while preserving space around the module, connector, enclosure, or cable channel.
The upgrade becomes easier to justify when RG174 uses a meaningful portion of the loss budget. At 900 MHz, a 3 meter example can reduce bulk cable loss by about 0.81 dB with the compared LMR100A construction. This amount may matter in a system with limited transmitter power, low received signal margin, or several additional connector transitions.
LMR100 is a compact jumper and short feeder option. It is not equivalent to the lower attenuation available from larger LMR cable sizes. If the cable run becomes long and the installation can accept a larger diameter, another cable size may provide a greater loss reduction.
FAQ
Conclusion
LMR100 normally offers lower attenuation and a more complete shielding structure than a typical RG174 cable while keeping a similar outside diameter. RG174 remains a suitable option for short, validated assemblies with enough loss margin, while LMR100 is more attractive when cable loss is using too much of the link budget or a compact shielding upgrade is required. The final selection needs to cover frequency, finished length, connector termination, routing, jacket version, and complete assembly test results. For a custom LMR100 or RG174 cable assembly, you can share the drawing, connector configuration, cable length, operating frequency, and insertion loss target with the Bafitop engineering team for review.