Coaxial Cable for Ham Radio: RG-58, RG-8X, and LMR-400 Compared
A radio, a good antenna, and a solid ground system get most of the attention when a station is planned, and the feedline connecting them gets whatever was already in the garage. That’s a mistake with real, measurable consequences: a poorly chosen coax run can throw away a meaningful fraction of transmit power before it ever reaches the antenna, and quietly do the same to received signals on the way back. This guide compares the three cable types most hams actually choose between — RG-58, RG-8X, and LMR-400 — and explains why the “right” choice depends on band, run length, and how the cable will be used, not on which one is cheapest at the local shop.
Why Cable Choice Matters More Than It Looks
Every coaxial cable has a loss figure, expressed in decibels per unit length, that increases with frequency. A cable that performs acceptably on 80 meters can be a genuinely poor choice on 10 meters or on VHF/UHF, even at the same physical length. The effect compounds: loss in the feedline attenuates the outgoing signal, and attenuates the incoming signal by the same amount, so a lossy run hurts both transmit and receive performance simultaneously. On a short run to a nearby vertical the difference between cable types might be negligible. On a run from an HF rig up to a tower-mounted antenna, or from a base station out to a rooftop VHF/UHF antenna, the difference between cable types can be the difference between a competitive station and a mediocre one.
How Coax Loss Actually Works
Three factors drive how much signal a coax run loses: frequency, cable length, and the cable’s own construction (conductor size, dielectric material, and shield quality). Loss rises with frequency for every cable type — this is why a run that’s fine on 40 meters can be lossy on 2 meters — and rises linearly with length, so doubling the run roughly doubles the loss in dB. Cable diameter matters because a larger center conductor and dielectric generally support lower loss, which is exactly why cables like LMR-400 are noticeably thicker and stiffer than RG-58.
Manufacturer datasheets publish loss figures in dB per 100 feet (or dB per 100 meters) at specific test frequencies, and free online coax loss calculators let you plug in your actual run length and frequency to get a real number rather than a rule of thumb. Given how much loss figures vary between manufacturers and cable grades even within the same nominal cable type, checking the actual datasheet for the cable you’re buying is worth the five minutes before committing to a long run.
RG-58, RG-8X, and LMR-400 Compared
| Cable | Relative Diameter | Relative Loss | Flexibility | Typical Use |
|---|---|---|---|---|
| RG-58 | Thin (~5 mm) | Highest of the three, especially above HF | Very flexible | Short patch leads, handheld accessories, temporary or portable runs |
| RG-8X | Medium (~6–7 mm) | Moderate — noticeably better than RG-58, still lossy at VHF/UHF over long runs | Flexible, easy to route | Short-to-medium HF runs, portable and field-day style setups |
| LMR-400 (and equivalents) | Thick (~10 mm) | Lowest of the three at all amateur bands | Stiff, larger bend radius needed | Long HF runs, VHF/UHF, tower and rooftop feedlines |
The pattern holds across nearly every cable family, not just these three: thinner and more flexible generally means higher loss, and lower loss generally means thicker and stiffer. There’s no cable that is simultaneously the thinnest, most flexible, and lowest-loss option — the trade-off is fundamental to how coax works, not a gap in the market.
RG-58: Convenience Over Performance
RG-58 earns its place through flexibility and low cost rather than electrical performance. For a two-foot jumper between a rig and a tuner, or a patch lead for a handheld accessory, its higher loss per foot barely registers because the run is so short. Used as a primary feedline for anything beyond a few meters, especially above the HF bands, its losses become the limiting factor in the station’s actual performance.
RG-8X: The Middle Ground
RG-8X sits deliberately between RG-58 and full-size cables like LMR-400, and it’s a genuinely reasonable choice for many home stations: HF runs of moderate length where flexibility around a mast base or through a wall entry matters, or portable and field setups where a full run of LMR-400’s stiffer, heavier cable would be awkward to coil and carry.
LMR-400: The Low-Loss Standard
LMR-400 and its equivalents (branded versions exist from multiple manufacturers with essentially the same electrical specification) are the default recommendation once a run gets long or the frequency gets high. The tradeoff is physical: it’s noticeably stiffer, has a larger minimum bend radius, and needs different connectors than the smaller cables, which matters when routing it through existing conduit or around tight corners.
Connectors: PL-259/SO-239 vs N-Type
Cable choice and connector choice are linked, and getting them mismatched causes more real-world problems than the cable’s raw loss figure ever does. The traditional PL-259/SO-239 pair (commonly called “UHF” connectors) is inexpensive and easy to install with basic tools, but it’s not a true 50-ohm connector by design and its performance degrades more than an N-type connector’s does at higher frequencies. For HF-only stations this is rarely a practical issue. For VHF/UHF work, especially at longer distances or with weak-signal modes, an N-type connector is the better match electrically, and it also seals against moisture more reliably at an outdoor connection point.
Whichever connector is used, a poorly soldered or crimped connection is a far more common source of loss and intermittent faults than the cable itself. A cheap high-quality connector properly installed will consistently outperform an expensive connector installed carelessly.
Matching Cable to Application
- Short jumpers and patch leads (under ~2 m): RG-58 is fine; its higher loss per foot is irrelevant over such a short distance.
- HF station, moderate run (shack to a nearby vertical or dipole feedpoint): RG-8X is a reasonable default, and it’s what most of the antenna guidance in our first-HF-antenna comparison assumes as a baseline feedline.
- Long HF run, or any VHF/UHF run: LMR-400 or an equivalent low-loss cable pays for itself in received and transmitted signal that would otherwise be lost in the feedline.
- Field/portable operation: weight and coiling matter as much as loss; a shorter run of RG-8X often beats a longer run of thick low-loss cable that’s a burden to carry and deploy.
A low feedline loss also doesn’t guarantee a clean SWR reading, since those two measurements describe different things about the line — see our guide to what an SWR meter tells you and what it hides for how they relate. Feedline choice also interacts with common-mode current on the outside of the shield, which is a separate problem from resistive loss and is addressed with chokes rather than a different cable — covered in depth in our guide to common mode chokes. A low-loss cable with unmanaged common-mode current can still cause RFI and pattern distortion regardless of how good the cable’s published loss figures are.
Common Mistakes
| Mistake | Consequence | Fix |
|---|---|---|
| Using RG-58 for a long VHF/UHF run | Large fraction of signal lost before reaching the antenna | Step up to LMR-400 or equivalent for long or high-frequency runs |
| Assuming SWR alone reveals feedline problems | A lossy cable can mask a bad SWR reading at the radio end | Measure SWR and loss separately; a good match doesn’t mean a good feedline |
| Mixing connector types with adapters at every joint | Each adapter is a potential loss and failure point | Standardize on one connector type per run where practical |
| Ignoring the minimum bend radius on stiff cable | Kinked dielectric permanently degrades performance at the kink | Respect the manufacturer’s minimum bend radius, especially on LMR-400 |
| Buying unbranded “LMR-400 equivalent” without checking specs | Some budget cables underperform the nominal spec | Check the actual datasheet loss figures, not just the printed cable name |
Frequently Asked Questions
Does cable choice matter if my run is very short?
Much less. Loss accumulates with length, so a two-meter jumper of RG-58 loses very little compared to the same cable run over twenty meters. Short runs are exactly where RG-58’s flexibility and low cost are a reasonable trade.
Is LMR-400 always the best choice?
Electrically, for long runs or higher frequencies, generally yes. Practically, its stiffness and larger bend radius make it awkward for portable use or tight routing, which is why RG-8X remains a common and reasonable choice for many home HF stations.
Can I mix cable types in one run?
You can, using an appropriate connector adapter or barrel at the junction, but every additional connector is a potential loss and failure point. If a run genuinely needs to change cable types partway, use quality connectors at the joint and weatherproof any outdoor junction.
Does connector type affect SWR readings?
A poor connector installation can introduce reflections that show up as SWR, separate from the cable’s own loss. A correctly installed PL-259 works fine at HF; its main weakness shows up at higher frequencies and in outdoor weatherproofing, not in typical HF SWR readings.
How do I know the real loss figure for my specific run?
Use the manufacturer’s published dB/100 ft (or dB/100 m) figure for your operating frequency and plug your actual run length into a coax loss calculator, several of which are freely available online. Don’t rely on a cable name alone, since loss figures vary between manufacturers even for nominally identical cable types.
Does thicker cable always mean lower loss?
As a general rule yes, because a larger center conductor and dielectric reduce resistive and dielectric loss. It’s not an absolute rule across every product on the market, which is another reason to check the actual datasheet rather than judging by cable diameter alone.
Is it worth upgrading an existing RG-58 run to LMR-400?
If the run is long, or feeds a VHF/UHF antenna, or feeds anything on the higher HF bands, the upgrade often produces a noticeable, measurable improvement in both transmitted and received signal. For a short run or a low-frequency-only application, the improvement may not justify the cost and installation effort.
The Bottom Line
Coax is not a place to economize by default. Loss compounds with both frequency and length, and it degrades transmit and receive performance equally, which makes it one of the more consequential and most overlooked parts of a station. RG-58 earns its place in short jumpers and portable patch leads, RG-8X is a solid middle-ground choice for moderate HF runs, and LMR-400 or an equivalent low-loss cable is the right call once a run gets long or the frequency climbs into VHF/UHF territory. Match the cable to the actual run, check the datasheet rather than guessing from the cable’s name, and pair it with quality, correctly installed connectors — the feedline should be the part of the station that never shows up as a limiting factor.