Why We Ditched RG58 for LMR240/KMR240 in LoRa and Helium Deployments

We get this question a lot — usually from someone who just spent three weekends wrestling with a Helium hotspot that keeps dropping off the network, or an engineer whose outdoor LoRa node is showing RSSI numbers that make no sense given the antenna they installed.

Nine times out of ten, the cable is the problem. And nine times out of ten, the cable is RG58.

Let's talk about why we don't use it anymore, and what we use instead.

 

RG58 Is a Fine Cable. For the Wrong Application.

RG58 has been around since the 1950s. It's cheap, flexible, widely available, and perfectly decent for short indoor runs at lower frequencies — think ham radio in a shack, a bench test setup, patching between two pieces of lab gear.

The problem is that LoRa and Helium deployments are almost never that. You're typically running cable up a mast, through a wall penetration, across a rooftop, or down from a chimney mount. Runs of 5 to 15 meters are completely normal. And you're working at 868 MHz or 915 MHz — which is where RG58 starts to hurt you in a measurable way.

At 900 MHz, RG58 loses roughly 0.6–0.8 dB per meter depending on the specific cable and how it's terminated. That sounds small until you do the math. A 10-meter run costs you 6–8 dB. That's more than one S-unit. That's the difference between a hotspot that witnesses 40 beacons a day and one that witnesses 12.

You don't buy a good antenna to then burn half its gain in the cable.

 

What LMR240 Actually Does Differently

LMR240 (and its metric equivalent, KMR240) is a low-loss 50Ω coaxial cable designed specifically for the frequency range where modern IoT runs — 400 MHz to 2.4 GHz. The construction is different in two important ways:

Larger center conductor. LMR240 uses a solid aluminum-clad copper center, significantly thicker than RG58's solid copper wire. More conductor cross-section means lower resistive losses, especially as frequency goes up.

Foam dielectric. Instead of solid polyethylene, LMR240 uses foam dielectric with a higher velocity of propagation (~83% vs ~66% for RG58). Less energy is absorbed by the insulation on every cycle.

The result: at 900 MHz, LMR240 loses around 0.22–0.26 dB per meter — roughly a third of RG58's loss. On that same 10-meter run, you're giving up 2.2–2.6 dB instead of 6–8 dB. That's a real, measurable improvement that shows up in your Helium earnings dashboard and your LoRa coverage maps.

Here's a quick reference if you're sizing up a deployment:

 

Cable	Loss @ 900 MHz	5m run	10m run	15m run
RG58	~0.70 dB/m	3.5 dB	7.0 dB	10.5 dB
LMR240 / KMR240	~0.24 dB/m	1.2 dB	2.4 dB	3.6 dB

 

Keep in mind these are approximate figures for terminated cables at room temperature. Actual loss varies with connector quality, cable age, and whether you've properly weatherproofed your connections.

 

The Termination Factor (This Is Where People Mess Up)

A good cable terminated badly is a bad cable. We've seen pristine LMR240 runs completely undermined by a poorly crimped SMA connector or a PL-259 that someone soldered with too much heat and wicked solder into the braid.

A few rules that matter:

Use the right connector for the cable. LMR240 is 0.24" OD. It requires connectors spec'd for that diameter. Trying to crimp an RG58 connector onto LMR240 is a common mistake — the crimp ring won't seat correctly, and you'll get a connector that looks fine but has a 1–2 dB insertion loss problem you'll never diagnose without a VNA.

Weatherproof everything outdoors. Even "outdoor rated" connectors will corrode over 12–18 months without self-amalgamating tape or a proper gel-filled boot. Oxidized center pin contact? Another dB gone.

Check your SWR after installation. If you don't have a VNA or antenna analyzer on hand, at minimum use an app like RF Signal Tracker or your gateway's built-in RSSI reporting to verify the system is performing as expected before you button everything up.

 

When RG58 Is Still Fine

To be fair: if your cable run is under 2 meters and you're doing a bench evaluation or an indoor proof-of-concept, RG58 is perfectly usable. The losses are small enough that they don't matter. It's also significantly more flexible, which can matter in tight enclosures.

We still stock RG58 assemblies for exactly these use cases. But for anything going on a rooftop, a mast, or a pole — use LMR240. The upgrade cost is minor compared to a hotspot that underperforms for its entire service life.

 

Bottom Line

If you're deploying LoRa or Helium hardware and your cable run is longer than 2 meters, LMR240 or KMR240 is the correct choice. It's not exotic, it's not expensive, and the performance difference is real and measurable — not theoretical.

The most common thing we hear from customers after switching is: "I didn't realize the cable was the problem the whole time."

It usually is.

 

Shop LMR240 / KMR240 Cable Assemblies →

 

Have a specific deployment question? Drop us a line at rflinker@onelinkmore.com — we're usually pretty quick.