Quick answer: Coaxial cable carries a signal on one centre conductor with the return on a surrounding shield, at 75 ohm. Twisted pair carries it as a voltage difference between two identical conductors, at 100 ohm, with no shield in the unshielded version. Coax wins on shielding and on carrying power alongside video, which is why satellite and cable television still use it. Twisted pair wins on cost, connector density and Power over Ethernet, which is why offices and homes are wired with it.
The two are not competing for the same job so much as dividing it. A building often has both: twisted pair to every desk and coax to every television position. Understanding why makes it easier to decide which one to extend, and which one to replace when a service changes.
Two geometries, two impedance standards
Coax: shield as return
In coax the signal travels on the centre conductor and returns on the shield, which also blocks external fields. Because the shield completely surrounds the conductor, the geometry is stable and the impedance is easy to hold at 75 ohm, which is the compromise that minimises loss for broadband signals. The cost is that one cable carries one signal.
Twisted pair: difference as signal
Twisted pair uses two conductors carrying equal and opposite signals; the receiver subtracts them, so noise picked up equally on both cancels. Twisting keeps the pair’s exposure symmetrical. Four pairs in one jacket give four channels, which is why one cable can carry gigabit in both directions and still have room for PoE.
Bandwidth, distance and power
| Property | RG6 coax | Cat6a twisted pair |
|---|
| Impedance | 75 ohm | 100 ohm |
| Usable bandwidth | Up to 3 GHz | 500 MHz |
| Typical reach | 100 m for TV, km for RF | 100 m channel |
| Signals per cable | One broadband channel | Four pairs, bidirectional |
| Power delivery | Yes, up to about 60 V DC | PoE up to 90 W |
Why coax still owns television
Shielding in a hostile band
Satellite intermediate frequencies run from about 950 MHz to 2.15 GHz, and terrestrial television sits below 700 MHz. In that range, unshielded twisted pair leaks and picks up interference. Coax’s continuous shield keeps the signal in and the interference out, which matters when the cable runs beside mains or through a roof space full of electrical noise.
One cable, signal plus power
A satellite receiver powers the LNB on the same coax that carries the signal, and masthead amplifiers are fed the same way. That single-cable model is convenient on a roof, where running a separate power pair would need another weatherproof entry.
Why twisted pair owns data
Twisted pair is cheap, terminates into a small plastic plug, and supports Power over Ethernet up to 90 W, which powers cameras, access points and phones without a local supply. A structured cabling system also gives every outlet the same connector, so a phone point can become a data point without rewiring. Coax cannot match that flexibility: one cable, one service, and a connector that nobody wants on a desk.
Where both exist, keep them separate rather than adapting one into the other. MoCA runs ethernet over coax and works well, but it depends on the coax plant being healthy; the RG6 cables overview covers what a healthy drop looks like. For data, the Cat6 LAN cable page covers the common choice, and the Ethernet patch leads guide covers the cords that finish the link.
Adapters that convert one to the other
Media converters and MoCA adapters exist because buildings rarely match their occupants. A media converter joins fiber to twisted pair at a fixed speed and needs power at one end; a MoCA adapter joins coax to twisted pair and shares the coax plant with television services. Neither is a passive part, and both add a device that can fail. Where the run is new, install the cable the service needs rather than an adapter chain, because adapters accumulate power supplies, latency and a second point of failure in a cupboard nobody checks.
Distance also separates them. Coax carries a signal for a hundred metres with acceptable loss at television frequencies and for kilometres in radio systems, while twisted pair stops at a hundred metres for ethernet. That is why a campus backbone is fiber, a building riser is often coax for video and twisted pair for data, and a desk is twisted pair only. The cable follows the service, and the service decides the connector.
Practical scenarios
- Aerial distribution to six rooms: star-wire RG6 from a splitter, not daisy chained, and keep the splitter losses inside the signal budget.
- Home office desk: Cat6 to a wall outlet and a patch cord to the laptop; coax there is useless unless a television is also planned.
- Camera on a mast 30 m away: coax if the camera is analogue, twisted pair with PoE if it is IP; the choice follows the camera, not the cable price.
- Old building with only coax: MoCA adapters give a usable 1 Gbit/s backbone without new cable, provided there are no splitters with the wrong frequency range in the path.
FAQ
Can I run ethernet over coaxial cable?
Yes, with MoCA adapters, which modulate ethernet onto the coax and typically deliver up to 1 Gbit/s on a clean plant. It is not the same as plugging an RJ45 into coax, and it requires 75 ohm terminations and splitters rated for the MoCA band.
Why is coax 75 ohm and twisted pair 100 ohm?
Impedance is set by geometry. Coax at 75 ohm minimises loss for broadband signals; twisted pair at 100 ohm balances loss, crosstalk and connector design for data. Neither is better in general; each suits the signal it was designed to carry.
Is twisted pair immune to interference?
Not immune, but resistant: the differential pair cancels noise that arrives equally on both conductors. A shield adds protection but must be bonded at both ends to work. Unshielded cable run parallel to mains for several metres will pick up noise regardless of the twist.
