LMR-400 vs RG-58: Which Coax Cable Should You Use?
LMR-400 and RG-58 are both 50-ohm coaxial cables, but they perform very differently. RG-58 is a classic flexible cable that has been used in amateur radio, CB, and test equipment for decades. LMR-400 is a modern low-loss feedline engineered for base stations, cellular boosters, and long antenna runs. Choosing the wrong one can cost you multiple S-units on receive or limit your transmit range.
The Short Answer
LMR-400 is the clear winner for any run over 15 feet or any frequency above 30 MHz. RG-58 is only appropriate for short jumpers, portable operation, or low-frequency HF work where its higher loss is acceptable.
Key Differences at a Glance
- At 144 MHz, LMR-400 loses 1.5 dB/100ft vs RG-58's 3.9 dB — nearly 3× less loss
- At 440 MHz, the gap widens: LMR-400 at 2.7 dB vs RG-58 at 6.5 dB per 100ft
- LMR-400 handles 700W at 150 MHz; RG-58 is rated for only 150W
- RG-58 is far more flexible and easier to route in tight spaces
- LMR-400 costs about 2× more per foot but pays for itself in signal performance
Side-by-Side Specifications
| Specification | LMR400 Times | RG58 |
|---|---|---|
| Impedance | 50 Ohm | 50 Ohm |
| Frequency Range | DC – 6 GHz | DC – 1 GHz |
| Velocity Factor | 0.85 | 0.66 |
| Dielectric | Foamed PE | Solid PE |
| Shield | Aluminum foil + tinned copper braid | Tinned copper braid (95%) |
| Jacket | PE | PVC |
| Center Conductor | Bare copper clad aluminum, 2.74mm | Tinned copper, 19×0.18mm |
| Min. Bend Radius | 2.0 in (50mm) | 1.0 in (25mm) |
| Max Voltage | 600 VRMS | 1400 VRMS |
| Temperature Range | -40°C to +85°C | -40°C to +85°C |
| Weight | 5.0 lb/100ft | 2.2 lb/100ft |
Attenuation Comparison (dB per 100 ft)
| Frequency | LMR400 Times | RG58 | Difference |
|---|---|---|---|
| 100 MHz | 1.5 dB | 4.3 dB | +2.8 dB (RG58 worse) |
| 450 MHz | 3.3 dB | 9.8 dB | +6.5 dB (RG58 worse) |
| 900 MHz | 4.7 dB | 14.3 dB | +9.6 dB (RG58 worse) |
| 1.8 GHz | 6.8 dB | 21.5 dB | +14.7 dB (RG58 worse) |
| 2.4 GHz | 7.9 dB | 25.5 dB | +17.6 dB (RG58 worse) |
| 5.8 GHz | 13 dB | 44 dB | +31 dB (RG58 worse) |
When to Choose Each Cable
Choose LMR400 Times when:
- Base station feedlines over 15 ft
- VHF/UHF operation (144 MHz and above)
- Cellular booster installations
- Any run where signal loss matters
Choose RG58 when:
- Short jumpers under 10 ft
- Portable/QRP operation
- HF operation under 15 MHz
- Budget-constrained temporary setups
Frequently Asked Questions
Can I replace RG-58 with LMR-400?
Yes — LMR-400 uses the same 50-ohm impedance so it is a direct drop-in replacement. You will need to re-terminate the connectors since LMR-400 is thicker (0.405") than RG-58 (0.195"). The performance improvement will be immediately noticeable on VHF and UHF.
Is RG-58 good enough for ham radio?
For HF operation (under 30 MHz) and short runs under 15 feet, RG-58 is adequate. For VHF/UHF base stations or any run over 25 feet, the loss in RG-58 is significant enough that LMR-240 or LMR-400 is strongly recommended.
What connectors work with LMR-400?
LMR-400 is most commonly terminated with N-type, PL-259/UHF, and SMA connectors. The large diameter requires connectors specifically sized for 0.400" cable.
How much signal do I lose with RG-58 vs LMR-400?
On a 50-foot run at 144 MHz, RG-58 loses about 1.95 dB versus 0.75 dB for LMR-400 — roughly 1.2 dB difference. That is nearly half an S-unit, which is noticeable on marginal paths.
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