A coaxial cable carries electrical signals between devices while shielding those signals from outside interference. It’s the cable that connects your TV to a cable box, brings internet into your home from the street, links security cameras to a recording system, and connects antennas to radios. The design is simple but effective: a copper wire at the center carries the signal, and a metal shield wrapped around it keeps that signal clean.
How a Coax Cable Is Built
Every coaxial cable has four layers, each with a specific job. At the center is a copper conductor, the wire that actually carries your data or video signal. Surrounding that copper core is a plastic insulator called a dielectric, which keeps the center conductor physically separated from the outer layers and maintains consistent electrical properties along the cable’s length.
Around the insulator sits a braided copper mesh that acts as a shield. This is what makes coax different from a simple wire. The mesh creates what engineers call a Faraday shield: a grounded conductive barrier that routes stray electrical noise directly to ground before it can reach the signal inside. This same shield also prevents the signal from leaking out and interfering with nearby electronics. The outermost layer is a plastic jacket that protects everything from physical damage, moisture, and UV exposure.
The name “coaxial” comes from this layered design. The center conductor and the outer shield share the same axis, creating a symmetrical structure where the signal travels through the core and the return current flows through the shield. This concentric geometry is what gives the cable its interference resistance.
Where Coax Cables Are Used
The most common place you’ll find coax is in home entertainment and internet setups. Cable TV, satellite dishes, over-the-air HDTV antennas, and cable internet connections all rely on coaxial cable to move signals with minimal loss. If you have a cable modem, the thick round cable screwed into the back of it is coax.
Beyond the living room, coax shows up in security systems (connecting CCTV cameras to monitors), radio equipment (linking antennas to transmitters and receivers), Wi-Fi antenna extensions, GPS systems, and even automotive camera systems. In cars, a single coax cable can carry both video data and electrical power to a dashboard camera, eliminating the need for a separate power wire.
75-Ohm vs. 50-Ohm: Two Main Types
Coaxial cables come in two major categories based on their impedance rating, which describes how the cable handles electrical resistance. The distinction matters because using the wrong type degrades your signal.
75-ohm cables are optimized for low signal loss, making them the standard for video, audio, and broadcast applications. Your cable TV line, satellite dish connection, HDTV antenna, and home internet coax are all 75-ohm. If you’re receiving a signal rather than transmitting one, 75-ohm is almost always the right choice.
50-ohm cables balance signal loss with power handling, which makes them better for transmitting. Amateur radio operators, cellular tower equipment, wireless networking gear, and GPS antennas typically use 50-ohm coax. If the system includes a transmitter or antenna that sends signals out, it’s likely 50-ohm.
Common Cable Grades for Home Use
You’ll encounter three main grades of coax in residential and commercial settings, and the differences come down to thickness and signal reach.
- RG6 (18 AWG center conductor): The standard for cable TV, satellite TV, and internet connections. It handles long runs well and works for most home and small business installations, including outdoor use.
- RG59 (22 AWG center conductor): A thinner, older style suited for short distances. You’ll see it on security cameras, CCTV setups, and short TV antenna connections. It loses signal faster over distance than RG6, so it’s not ideal for long cable runs.
- RG11 (14 AWG center conductor): The thickest option, built for long-distance runs where signal quality needs to hold up over hundreds of feet. It’s common in outdoor commercial installations and trunk lines that feed into buildings.
How Coax Delivers Internet
Cable internet providers use coaxial cable for the “last mile” connection between their network and your home. The technology standard that makes this work is called DOCSIS. Most current cable internet plans deliver between 100 and 400 Mbps for downloads, with upload speeds around 35 Mbps, though some plans reach 1 Gbps downstream.
The newest version of this standard, DOCSIS 4.0, pushes coax capabilities significantly further: up to 10 Gbps downstream and 6 Gbps upstream. That puts coaxial internet in the same ballpark as fiber optic for raw speed, though fiber still has advantages in latency and consistency over long distances. Many cable providers use a hybrid setup where fiber carries the signal most of the way, then coax handles the final stretch into your home.
Why Signals Weaken Over Distance
Every coaxial cable loses some signal strength as the signal travels along its length. This is called attenuation, and two factors drive it: cable length and signal frequency. Higher frequencies lose strength faster, and longer cables lose more signal overall. This is why thicker cables like RG11 exist for long runs: the larger conductor has less electrical resistance, so the signal holds up better.
Signals travel through coax at roughly two-thirds the speed of light, or about 8 inches per nanosecond. For home distances this delay is negligible, but attenuation is noticeable. If you’re running coax across a large property, using the right cable grade and keeping connections tight makes a real difference in picture quality or internet speed.
How Coax Compares to Fiber Optic
Fiber optic cables use light instead of electrical signals, which gives them some inherent advantages. Fiber maintains its signal strength over much longer distances with minimal degradation, offers lower latency, and is less susceptible to electromagnetic interference. Fiber connections can reach 10 Gbps and beyond with consistent performance regardless of distance from the provider.
Coax, on the other hand, is already installed in most homes, costs less to maintain, and doesn’t require specialized equipment to terminate or splice. It’s also more physically durable in some environments. For most households, coaxial internet and TV service works perfectly well. The practical difference between coax and fiber only becomes significant for very high-bandwidth needs, long-distance runs, or situations where upload speed matters as much as download speed.
Connector Types and What They Fit
The connector on the end of a coax cable determines what equipment it plugs into. F-type connectors are the ones you’ll find on nearly every home TV, cable box, modem, and satellite receiver. They screw on for a secure, weatherproof connection.
BNC connectors use a twist-and-lock bayonet mechanism and are standard in professional video production, broadcast equipment, and security camera systems. They handle high-frequency signals without degradation and lock firmly in place, which matters when cables get bumped on a TV set or concert stage. SMA connectors are smaller and show up on Wi-Fi antennas, walkie-talkies, and handheld radios. N-type connectors are medium-sized, waterproof, and built for radio transmission equipment that lives outdoors.