A coaxial input is a round, threaded port on a TV, cable modem, audio receiver, or other device that accepts a coaxial cable to carry audio, video, or internet signals. You’ve almost certainly seen one: it’s the screw-on connection on the back of a television where you plug in cable TV or an antenna, or the port on a cable modem that connects to your internet service. The same basic technology also appears as a smaller RCA-style jack for digital audio on home theater equipment.
How a Coaxial Cable Works
A coaxial cable has a layered design built around a single copper wire at its center. That core conductor carries the actual signal. Surrounding it is a plastic insulator (solid or foam) that keeps the signal stable. Around that sits a metallic shield, usually woven copper braid or metallic tape, which blocks outside electrical interference from corrupting the signal. The outermost layer is a protective plastic jacket.
This “cable within a cable” design is where the name comes from: the inner conductor and outer shield share the same central axis, or “coax.” The shielding is what makes coaxial cables so reliable for carrying high-frequency signals over moderate distances without picking up noise from nearby electronics or power lines.
Common Types of Coaxial Inputs
Not all coaxial inputs look the same. The type of connector depends on what the input is designed to carry.
- F-type: The most familiar coaxial connector in homes. It’s the threaded, screw-on port found on TVs, cable boxes, satellite receivers, and cable modems. Nearly all residential TV and internet coaxial inputs use this connector.
- RCA: A push-on connector originally designed by the Radio Corporation of America. In audio systems, a single orange or black RCA jack often serves as a digital coaxial input for sending surround sound from a Blu-ray player or streaming box to a receiver.
- BNC: A twist-and-lock connector used in professional video, broadcast equipment, and security camera systems. You won’t typically find these in a living room, but they’re common in commercial AV setups.
Coaxial Inputs for TV and Internet
The coaxial input on your TV or cable modem receives a signal that travels over RG6 cable, the standard for modern residential installations. RG6 is built for high-bandwidth, high-frequency use. It has a thicker conductor and better shielding than the older RG59 cable, which was common decades ago but can’t handle the frequency demands of satellite TV or broadband internet. If your equipment operates above 50 MHz (and satellite and broadband signals do), RG6 is the right cable.
For internet specifically, coaxial inputs on cable modems use a standard called DOCSIS to convert the signal into usable data. The current version, DOCSIS 3.1, supports download speeds up to 10 Gbps and upload speeds up to 1 Gbps. Your actual speed depends on your internet plan and network conditions, but the coaxial input itself is not the bottleneck most people assume it is.
For television, the same coaxial input carries broadcast or cable channels. If you connect an over-the-air antenna to a TV’s coaxial input, it receives free local channels in HD without needing a cable subscription.
Coaxial Inputs for Audio
On home theater receivers, soundbars, and some TVs, you’ll find a digital coaxial input that looks like a standard RCA jack. This carries a digital audio signal using a format called S/PDIF, which can transmit surround sound up to 5.1 channels. The copper core carries the digital audio data while the metallic shield keeps interference out.
Digital coaxial audio inputs support sample rates up to 192 kHz, which matters if you listen to high-resolution music files. That’s a notable advantage over optical (Toslink) inputs, which top out at 96 kHz. Coaxial audio connections also tend to perform better over short cable runs. Optical connections, on the other hand, are immune to electrical interference and can solve ground loop hum, a low buzzing noise that sometimes occurs when multiple components share the same electrical circuit. For most people connecting a TV to a soundbar or receiver, either option works well.
Why 75 Ohms Matters
Consumer coaxial inputs for TV, internet, and audio are designed around a 75-ohm impedance standard. Impedance is essentially the cable’s resistance to the signal passing through it, and 75 ohms provides the lowest signal loss for the kinds of signals these devices use. It also happens to closely match the natural impedance of a standard TV antenna (73 ohms), making signal transfer between antenna and cable highly efficient.
If you’ve seen 50-ohm coaxial cables, those are designed for different purposes: radio transmitters, Wi-Fi equipment, and lab instruments where power handling matters more than minimizing signal loss. Using a 50-ohm cable on a 75-ohm input creates a mismatch that degrades your signal, so it’s worth checking if you’re buying cable for a home installation.
Cable Length and Signal Quality
Coaxial signals weaken over distance. For home TV and internet applications, shorter runs produce better results. Every additional foot of cable and every splitter in the line reduces signal strength. RG6 handles longer distances better than RG59 thanks to its thicker conductor and superior shielding, which combines foil (for blocking high-frequency interference) with braided wire (for lower-frequency protection).
If you’re running coaxial cable through your home, keep the total length from the source to the device as short as practical, and use the fewest splitters possible. Signal amplifiers can compensate for long runs, but they also amplify any noise in the line, so clean, direct connections are always preferable.
Identifying a Coaxial Input on Your Device
On the back of a TV, the coaxial input is typically labeled “ANT IN,” “CABLE IN,” or “RF IN.” It’s a single round port with a threaded outer ring and a small hole or pin in the center. On a cable modem, it’s usually the only round threaded port and may simply be labeled “COAX.” On an audio receiver, a digital coaxial input looks like a single RCA jack, often colored orange and labeled “COAXIAL IN” or “DIGITAL IN.”
If your device has both a coaxial and an HDMI input, HDMI carries both audio and video in a single cable and supports higher resolutions. Coaxial inputs remain useful for antenna TV reception, cable internet, and dedicated audio connections where HDMI isn’t an option or isn’t needed.