Coaxial cable, usually called coax, is a copper cable built in layers around a single central conductor: an inner conductor, an insulating layer, a metallic shield and an outer jacket. Because the shield surrounds the conductor on a shared axis, it keeps outside interference out and the signal in, which makes coax well suited to high-frequency signals. For business buyers it shows up mainly in three places: cable broadband service, in-building antenna systems, and older video surveillance wiring.
At a glance
- Coax is shielded copper cable designed for high-frequency signals, with a typical impedance of 75 ohms for video and broadband or 50 ohms for radio and antenna systems.
- Cable operators deliver broadband over coax using DOCSIS, usually in a hybrid fiber-coax network where fiber carries traffic to the neighborhood.
- In buildings, coax connects antennas and amplifiers in many distributed antenna systems and older analog CCTV cameras.
- Office data networks typically run on twisted-pair Ethernet cabling and fiber, not coax.
- Signal loss rises with distance and frequency, so cable type, connectors and installation quality matter.
What problem it solves
Coax was designed to carry high-frequency signals such as television and radio over distance without picking up interference or leaking signal. Cable companies built large networks of it to deliver TV to homes and businesses, then reused those networks for internet access. That installed base is why cable broadband is available at so many business addresses where fiber is not.
Inside buildings, the same properties make coax useful for radio systems that boost cellular coverage, and for decades it was the standard way to connect security cameras to recorders.
How it works
Construction. A copper or copper-clad center conductor carries the signal. A dielectric insulator keeps it at a fixed distance from the shield, which keeps the cable’s impedance consistent. The braided or foil shield blocks electromagnetic interference, and the jacket protects the cable physically. Cables with extra shield layers suit noisier environments.
Cable broadband. In a hybrid fiber-coax network, the operator runs fiber to a neighborhood node, then coax to each building. A cable modem at your site uses DOCSIS to send and receive data over the coax. Capacity in each segment is shared among the customers connected to it, and upload speeds are commonly lower than download speeds, though newer DOCSIS versions narrow that gap where operators deploy them.
Antenna systems. In a passive distributed antenna system, coax carries cellular radio signals between a donor source, amplifiers and indoor antennas. Larger systems often use fiber for long runs and coax for shorter ones.
Video. Analog CCTV cameras send video over coax to a DVR. Modern IP cameras use Ethernet, although adapters and hybrid systems can reuse existing coax during a transition.
When it matters for buyers
- When choosing internet access for a site. Cable broadband is often available and inexpensive, but is usually best-effort and asymmetric. It can suit small sites or a backup connection; compare it with fiber or dedicated access for primary links. See our internet access overview.
- When fixing indoor cellular coverage. Proposals for antenna systems specify coax runs and cable types, which affect performance and installation cost.
- When upgrading security cameras. Decide whether to reuse coax or recable with Ethernet as part of the project.
- When moving into a building. Old coax runs are common; knowing what is live and what can be removed avoids confusion with the network you actually need.
Questions to ask vendors
For cable broadband providers:
- What download and upload speeds are committed, and is the service best-effort or backed by an SLA?
- Is a static IP address available, and what does it cost?
- What are the repair times, and is business-grade support included?
For antenna system and cabling installers:
- Which cable types and connectors will you use, and why?
- How will you test and document signal levels after installation?
- Will you remove abandoned coax as part of the work?
How it differs from fiber
Fiber carries data as light through glass strands, while coax carries electrical signals through copper. Fiber supports much higher capacity over far longer distances and doesn’t pick up electrical interference, which is why carriers use it for backbones and increasingly run it directly to buildings as fiber to the premises (FTTP). Coax is cheaper where it is already installed and remains common for the last mile of cable networks. For a business buyer, the practical difference is usually in the service built on each: cable broadband over coax is typically shared and asymmetric, while fiber-based services more often offer symmetrical speeds and, for dedicated products, contractual commitments.