RG-58 vs LMR-400: Which Coax Should You Buy?

The most common question from ham operators setting up a new station or upgrading an existing one is straightforward: should I stick with RG-58 or spend more on LMR-400? The answer depends on your run length, your operating frequencies, and whether you're doing a temporary or permanent installation. This guide gives you the numbers to make the decision without guessing.

The Real Loss Numbers

Cable loss is measured in decibels per 100 feet. Loss increases with frequency, which is why a cable that's perfectly adequate for HF can be a serious problem on VHF and UHF. Here are representative figures for the cables commonly found in ham shacks:

Power Reaching Your Antenna

Loss numbers are more intuitive when converted to actual power. Here's how much power from a 100-watt radio reaches the antenna after 100 feet of each cable type at 144 MHz and 440 MHz:

At 440 MHz, RG-58 delivers only 20 watts out of 100 to the antenna. LMR-400 delivers 48 watts — more than double. On a 70cm repeater connection or a weak-signal EME path, that difference is the margin between making the contact and not.

When RG-58 Is the Correct Choice

RG-58 gets unfairly maligned. For the right applications it's excellent: it's flexible (minimum bend radius of about 1.5 inches), inexpensive, and at HF frequencies the loss difference versus premium cable is negligible for short runs. Specific situations where RG-58 is the right call:

• HF operation (below 30 MHz) with runs under 40 feet
• Portable and field day operations where flexibility and weight matter
• Indoor shack jumpers between radio, tuner, and antenna switch
• Budget installations where the antenna run is short
• Temporary setups that will be reconfigured frequently

RG-58 PL-259 to PL-259 Cable

When to Upgrade to LMR-400

LMR-400 is the go-to cable for permanent VHF/UHF installations, long outdoor runs, and any setup where signal performance matters. The foam polyethylene dielectric and bonded foil plus braid construction give it loss figures roughly 2.2× better than RG-58 at 144 MHz and 2× better at 440 MHz. Upgrade when:

• Operating on 2 meters (144 MHz), 70cm (440 MHz), or higher
• Any run over 30 feet for VHF/UHF
• Permanent outdoor installation to a roof, mast, or tower
• High-power operation (LMR-400 handles 700W at 150 MHz)
• Repeater or base station feedlines

LMR-400 PL-259 to PL-259 Feedline

Where RG-213 and RG-8X Fit

RG-213 and its thinner cousin RG-8X occupy a useful middle ground. They're more flexible than LMR-400 (LMR-400 has a minimum bend radius of 4 inches, which makes routing through tight spaces difficult), significantly better than RG-58, and still fairly affordable. RG-213 is a good choice for medium-length HF runs — 50 to 100 feet — where the stiffness of LMR-400 would be a problem and RG-58 loss is too high. It's also commonly used as the feedline from a manual tuner to a window-line antenna at medium power levels.

RFC400: The LMR-400 Alternative

RFC400 (also called Times Microwave LMR-400-equivalent or generic 400-series coax) has nearly identical electrical performance to LMR-400 — the loss figures in the table above are essentially the same. It uses the same construction: foam polyethylene dielectric, bonded foil shield, and braided outer conductor. RFC400 is sometimes more available or better priced than brand-name LMR-400, and it's an excellent choice for all the same applications. CoaxRF stocks both; you can order them in PL-259 or N-type terminations.

RFC400 PL-259 to PL-259 Feedline

LMR-600: For Long Tower Runs

LMR-600 is 0.59 inches in diameter — significantly thicker than LMR-400 (0.405 inches) — and its loss figures at VHF/UHF are roughly 40% better. For tower runs over 100 feet on 2 meters or 70cm, the difference is meaningful. A 150-foot run of LMR-400 at 440 MHz loses 4.8 dB; the same run in LMR-600 loses 3.0 dB. LMR-600 requires more planning: larger conduit, a minimum bend radius of 6 inches, and heavier connector hardware. But for a permanent high-performance installation, it's the right tool.

LMR-600 PL-259 to PL-259 Ultra Low-Loss Feedline

Flexibility and Bend Radius

Stiffness is a real consideration when routing cables through walls, conduit, and equipment bays. RG-58 has a minimum bend radius of about 1.5 inches — it'll go almost anywhere. LMR-400 needs at least 4 inches, which rules out many tight routing paths. LMR-600 requires 6 inches. If your cable run requires multiple tight bends in a cramped equipment bay, RG-213 or RG-8X may actually serve you better than LMR-400 despite lower electrical performance. A cable that's kinked has permanently damaged dielectric and higher loss than its spec.

Cost Comparison

For a 50-foot VHF/UHF run, the extra $40 for LMR-400 vs RG-58 buys you approximately 3.8 dB more signal — nearly a full S-unit on receive, and the difference between a solid contact and a lost one. Spending more on the cable and less on the antenna is almost always the wrong trade-off. Get your feedline right first.

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