{"id":3585,"date":"2026-10-22T00:37:18","date_gmt":"2026-10-21T16:37:18","guid":{"rendered":"http:\/\/www.thesoter.com\/blog\/?p=3585"},"modified":"2026-10-22T00:37:18","modified_gmt":"2026-10-21T16:37:18","slug":"what-is-the-attenuation-of-rf-coaxial-cable-4b31-e761e6","status":"publish","type":"post","link":"http:\/\/www.thesoter.com\/blog\/2026\/10\/22\/what-is-the-attenuation-of-rf-coaxial-cable-4b31-e761e6\/","title":{"rendered":"What is the attenuation of RF Coaxial Cable?"},"content":{"rendered":"

Hey, let\u2019s cut to the chase\u2014if you\u2019ve ever worked with RF gear (like cell towers, WiFi routers, or broadcast antennas), you\u2019ve probably noticed that sometimes signals just \u201cvanish\u201d before they reach their destination. No, it\u2019s not magic\u2014it\u2019s attenuation, and if you\u2019re buying RF coaxial cables, this is non-negotiable to understand. I\u2019m not here to hit you with stuffy textbook jargon; I\u2019m a coaxial cable supplier, and I see exactly how muddled this gets for folks new to RF or even seasoned pros who just want to pick the right cable without overcomplicating it. RF Coaxial Cable<\/a><\/p>\n

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First, let\u2019s keep it simple: attenuation is just signal loss over distance. Yeah, that\u2019s the plain-spoken version. For RF coaxial cables, that loss isn\u2019t the same for every frequency\u2014super important, because if you\u2019re running a 5G network (think mmWave, which uses crazy high frequencies), your loss will be way worse than if you\u2019re doing a walkie-talkie link on a low VHF band. Let\u2019s break down the two big reasons this happens, because knowing why helps you pick the right cable instead of just grabbing whatever\u2019s cheapest.<\/p>\n

The first big culprit is conductor loss. Coax has two metal parts, right? The inner conductor (that thin wire running down the middle) and the outer shield (the metal mesh or foil around it). Both of these don\u2019t conduct RF electricity perfectly. Even copper, which is the best common conductor, has something called skin effect when you\u2019re dealing with RF. Wait, what\u2019s skin effect? Picture a crowd\u2014when you get hyped, everyone pushes to the front. For RF signals, the electrical current doesn\u2019t flow through the whole metal conductor; it only flows in a thin \u201cskin\u201d right at the surface of the inner conductor and the inner surface of the outer shield. The higher the frequency, the thinner that skin gets. So for mmWave, that skin is super tiny\u2014so even a little bit of resistance in that thin layer adds up to way more loss than at, say, 900 MHz. That\u2019s why a cable that works fine for a 2.4 GHz WiFi setup will suck for a 28 GHz 5G link; the conductor loss skyrockets at higher frequencies. As a supplier, I see this all the time\u2014customers come to us saying \u201cmy 5G signal is weak\u201d and they\u2019re using a cheap LMR-400 cable meant for lower frequencies, not a low-loss variant made for mmWave.<\/p>\n

The second big one is dielectric loss. Between the inner and outer conductor, there\u2019s that plastic stuff\u2014dielectric. It\u2019s not just there to keep the inner wire centered; it\u2019s also part of the signal path. RF signals pass through the dielectric, and every time they do, a tiny bit of energy gets turned into heat. Again, frequency is the villain here\u2014higher frequencies mean the signal\u2019s electric field switches back and forth faster, so the dielectric can\u2019t keep up, and more energy is lost as heat. What kind of dielectric matters here? If you have a solid polyethylene (PE) dielectric, that\u2019s basic, cheaper, has a bit more loss. If you use foamed PE (air bubbles inside the plastic), that cuts loss because air has way lower loss than plastic. Even fancier stuff like PTFE (Teflon) is used for super high frequencies, since it has way less dielectric loss at mmWave bands. I always tell customers: if you\u2019re running a cable long distance at high freq, splurge on foamed or PTFE dielectric, not the solid PE junk.<\/p>\n

Wait, there\u2019s also another thing that causes extra attenuation, right? Not the cable itself, but how you install it. Bending a coax too tight\u2014like, way under the minimum bend radius listed on the spec sheet\u2014crushes the dielectric and messes up the conductor shape. That creates \u201cmicro-currents\u201d and extra signal loss. Also, bad connections: if you don\u2019t crimp the connector right, or leave gaps in the outer shield, you get reflections that add to the total loss. I\u2019ve had a customer bring a cable back that \u201clost half the signal\u201d and it turned out they bent it around a sharp corner with a 1-inch radius\u2014their cable\u2019s min bend radius was 4 inches. Fixing that cut their loss by 60% without even replacing the cable. So attenuation isn\u2019t just about the cable\u2019s inherent spec; installation kills it too.<\/p>\n

Now, let\u2019s talk about how attenuation is measured, because cable specs are all in numbers. The standard unit is decibels per 100 meters (dB\/100m) or sometimes decibels per foot (dB\/ft) for shorter runs. The lower that number, the less loss you get. For example, a basic LMR-400 might have a loss of ~6.5 dB at 2.4 GHz and ~15 dB at 10 GHz. A low-loss variant like LMR-400 Ultra Low Loss (ULL) would be like ~5.5 dB at 2.4 GHz and ~12 dB at 10 GHz. That might not sound like a big difference, but let\u2019s do the math: if you\u2019re running a 100-meter cable at 10 GHz, the basic one loses 15 dB, the ULL loses 12 dB. Why does that matter? A 3 dB loss is half your signal power\u2014so that ULL cable lets you keep twice the signal at the end. For a cell tower, that means you need less power from the antenna, or you can cover a wider area. For IoT sensors in a factory, that means your sensor stays connected instead of dropping data because the signal is too weak.<\/p>\n

Here\u2019s the part that most people get wrong: you can\u2019t just use the same attenuation spec for every frequency. Let\u2019s take an example: a customer building a 5G small cell at 28 GHz came to me last year. They picked a cheap LMR-200 cable because it\u2019s thin and easy to run. I told them, \u201cWait, LMR-200 at 28 GHz has ~30 dB per 100m\u2014 that\u2019s almost all your signal gone.\u201d They argued \u201cit\u2019s low loss, right?\u201d No, low loss is relative to its frequency range. LMR-200 is for lower frequencies; at mmWave, even a smaller diameter cable has higher attenuation because of skin effect and dielectric loss at those high freqs. We switched them to an LMR-400 ULL, which was thicker, but only had ~18 dB per 100m at 28 GHz\u2014half the loss. They saved their project from being a total flop, and they\u2019ve been a repeat customer ever since. That\u2019s the kind of call I make as a supplier\u2014don\u2019t just go by the \u201clow loss\u201d label; check the frequency point you\u2019re using.<\/p>\n

Also, attenuation isn\u2019t all bad. Wait, hear me out\u2014sometimes you need a little attenuation. Like, if you\u2019re testing RF gear, or tuning a system to avoid signal overload. But that\u2019s using attenuators, which are different from the transmission cable we\u2019re talking about. The attenuation in the coaxial transmission cable is what you want to minimize, not control, for most applications.<\/p>\n

Now, let\u2019s clear up a myth: thicker cables don\u2019t always mean less attenuation. Wait, that sounds counterintuitive, right? But it\u2019s about matching frequency. A super thick LMR-600 has lower loss at high frequencies than a thin LMR-200, yes. But if you\u2019re running a 900 MHz walkie-talkie setup, a thin LMR-195 cable has barely any more loss than LMR-400, and it\u2019s way easier to route through tight spaces, like walls or office ceilings. So it\u2019s a trade-off: thicker = less loss for high freq, thicker = stiffer, harder to install, more expensive. Thinner = easier to run, cheaper, but more loss at high freq. That\u2019s where I come in\u2014 I ask customers questions: What frequency are you running? How long is the cable run? Where is it going (sharp bends, tight spaces, outdoor weather)? Then I match them to the right cable, not just the priciest or cheapest.<\/p>\n

Wait, outdoor vs indoor\u2014does that affect attenuation? Not directly, but the cable\u2019s build does. Outdoor cables have weatherproof jackets (like LSZH or UV-resistant PE) that don\u2019t change the inherent loss, but they do mean the cable doesn\u2019t get damaged, which would add extra loss from dents or cracked shields. Indoor cables can use lighter jackets, which is fine, but don\u2019t use indoor cables outside\u2014rain and sun will ruin them, and then your loss will spike. I see that mistake all the time too.<\/p>\n

Let\u2019s circle back to why this is critical for you, the person buying RF coax. If you ignore attenuation, you end up with:<\/p>\n