At matching test frequencies, LMR400-family cable loses noticeably less per 100 feet than RG6, as reported on each cable’s own manufacturer datasheet: roughly 3.9 dB versus 5.79 dB at 900 MHz, 5.7 dB versus 8.43 dB at 1800 MHz, and 6.8 dB versus 9.97 dB at 2500 MHz. That’s close to half the loss at the higher end of the cellular band. The trade-off isn’t free: LMR400 is thicker, stiffer, uses a different connector standard, and typically costs more per foot than RG6. Whether that trade is worth it comes down almost entirely to how long your cable run is, which we work through below with real numbers rather than a blanket recommendation.
The Numbers, Side by Side
These figures come from two real manufacturer datasheets, compared at the frequency points both sheets happen to list. One is CommScope’s published specification for its 5781 BKRL RG6 quad-shield cable. The other is Times Microwave’s LMR-400-DB (the outdoor-rated, double-jacketed version of LMR400), as distributed and published by Fairview Microwave. Both figures are quoted as reported on those datasheets, not estimated or interpolated.
| Frequency | RG6 (CommScope 5781 BKRL), dB/100 ft | LMR-400-DB (Times Microwave), dB/100 ft | Difference |
|---|---|---|---|
| 900 MHz | 5.79 | 3.9 | 1.89 dB |
| 1800 MHz | 8.43 | 5.7 | 2.73 dB |
| 2500 MHz | 9.97 | 6.8 | 3.17 dB |
Two things stand out. First, LMR400 loses less at every frequency where both sheets have a listed point, consistent with its reputation as a lower-loss cable. Second, the gap between the two widens as frequency climbs. That second point matters more than it might look: it means the cable choice matters more at the higher end of the cellular spectrum than at the lower end, which changes how much weight to give this decision depending on which bands your carrier and device actually use.
Why LMR400 Loses Less
The difference comes down to construction, not marketing. LMR400 has a larger-diameter center conductor and a different dielectric construction than RG6, and a larger conductor generally means less resistive loss carrying the same signal. This is also why LMR400 is physically thicker (roughly 0.4 inches in diameter) and stiffer than RG6, which is thinner and more flexible. The lower loss is a direct consequence of the cable being built bigger and to a different mechanical standard, not an unexplained brand difference.
Which One Is Actually In Your System
This isn’t purely a free choice for most installs, because the two cable types are typically tied to different connector standards and different classes of equipment.
RG6 is the cable most consumer and residential booster kits ship with, terminated in F-connectors, running at 75 ohms. If you bought a standard home or small-office booster kit, RG6 with F-connectors is very likely what’s already in the box.
LMR400 runs at 50 ohms and is typically terminated with N-connectors, and it’s the cable more commonly specified for commercial-grade booster installations and longer outdoor runs. Swapping between the two isn’t as simple as buying a different spool of cable, because the connector type and impedance need to match what your booster’s ports and antennas actually expect. Check your unit’s manual for the connector type and impedance it specifies before assuming either cable is a drop-in option for your system.
When the Difference Actually Matters
Here’s where a generic “LMR400 is better” recommendation stops being useful, because the real-world impact depends entirely on how much cable you’re running.
Short run (20 feet, 1800 MHz): RG6 costs roughly 1.7 dB; LMR400 costs roughly 1.1 dB. The difference is about half a dB, which is close to negligible for most installs.
Medium run (50 feet, 1800 MHz): RG6 costs roughly 4.2 dB; LMR400 costs roughly 2.9 dB. The gap, about 1.3 dB, is starting to be worth considering if your outdoor signal is already marginal.
Long run (100 feet, 1800 MHz): RG6 costs roughly 8.4 dB; LMR400 costs roughly 5.7 dB. That’s a meaningful chunk of a typical booster’s gain budget, and the roughly 2.7 dB gap between the two cables is no longer a rounding error.
The pattern is straightforward: the longer your run, the more a lower-loss cable actually buys you. A short indoor cable run from an attic-mounted booster to a nearby antenna rarely justifies switching cable types. A long outdoor run from a roof antenna down to a booster in a basement or utility closet is exactly the situation where the lower-loss option earns its keep.
A Decision Table by Run Length
| Cable run length | Practical takeaway |
|---|---|
| Under 25 feet | The difference between RG6 and LMR400 is small enough that other factors (what your kit ships with, ease of installation) usually matter more |
| 25 to 75 feet | Worth checking your actual numbers, especially if your outdoor signal is borderline rather than strong |
| Over 75 feet | The lower-loss option is meaningfully worth it, particularly at the higher end of the cellular band |
Physical and Practical Differences Beyond Loss
Loss per foot isn’t the only difference worth knowing before you choose.
Flexibility. RG6 bends easily and is simple to route through tight spaces, attic joists, or wall cavities. LMR400’s larger diameter and stiffer construction make it harder to route through the same spaces and require a wider minimum bend radius.
Connectors and weatherproofing. N-connectors, used with LMR400, generally provide a more robust weatherproof seal than the F-connectors used with RG6, which matters more for outdoor runs exposed to the elements over years.
Cost per foot. LMR400 typically costs more per foot than RG6, reflecting its heavier construction. This is a budget consideration, not a performance one, and worth weighing against how much the loss difference actually matters at your run length using the table above.
The Regulatory Note
Consumer signal boosters are certified as a complete system, which includes the cable and connector configuration the unit shipped with or was tested with. Swapping cable types is generally a lower-stakes change than swapping antennas, but if your kit specifies a particular cable and connector standard, deviating from it can affect performance in ways the manufacturer didn’t test for. When in doubt, check your unit’s manual, and see is a cell phone signal booster legal for the fuller picture on what modifying a certified system does and doesn’t allow.
Cable type is one piece of a longer chain. Where the antenna is mounted in the first place changes how long a cable run you need to begin with, covered in attic mount versus roof mount, and the general principles of reading any cable’s datasheet, including how length and frequency combine, are covered in coax cable loss, explained. Getting the antenna placement right in the first place matters at least as much as cable choice; see the common mounting mistakes that cost signal before the cable is even involved.
FAQ
Does LMR400 always beat RG6 for a signal booster?
On loss per foot, yes, at every matching frequency on the datasheets compared here. Whether that difference is worth the added cost and stiffness depends on your cable run length; for short runs the difference is close to negligible, for long runs it becomes meaningful.
How much less signal does LMR400 lose compared to RG6?
Based on the manufacturer datasheets compared here, roughly 1.9 dB per 100 feet less at 900 MHz, 2.7 dB per 100 feet less at 1800 MHz, and 3.2 dB per 100 feet less at 2500 MHz. The gap widens at higher frequencies.
Can I use LMR400 with a consumer booster that ships with RG6 connectors?
Not without changing connectors and confirming impedance compatibility, since consumer kits are typically built around RG6’s 75-ohm F-connector standard while LMR400 runs at 50 ohms with N-connectors. Check your unit’s manual before mixing cable types.
Does cable type matter for a short indoor run?
Not much. Over a run of 20 to 25 feet, the difference between RG6 and LMR400 is well under a decibel at most cellular frequencies, small enough that other factors usually matter more for a short indoor run.
Which cable does my booster actually need?
Check your unit’s manual and the connectors it ships with. Most consumer and residential kits use RG6 with F-connectors; commercial-grade systems more commonly specify LMR400 with N-connectors. Match what the manufacturer specifies rather than assuming either cable is interchangeable.
