Quick Answer: Coax is 75 ohm, single conductor, and carries one wideband signal per cable; twisted pair is 100 ohm, four balanced pairs, and carries a bidirectional baseband link. RG-6 handles 1 GHz with about 18 dB of loss per 100 metres and runs 60 metres (200 ft) to a television; Cat 6 carries 250 MHz over 100 metres and delivers data plus up to 90 W of power. Use coax for video, satellite and legacy camera runs, twisted pair for anything with an IP address.
Impedance, not bandwidth, is the first decision. A 75 ohm source expects a 75 ohm load, and a 100 ohm twisted pair cannot be substituted without baluns at both ends and a loss penalty. Once that is settled, the second decision is whether the run needs power at the far end, which only twisted pair delivers cleanly.
What each cable is built to do
Coax puts the signal on a centre conductor inside a dielectric, with a foil and braid screen as the return path, so the field stays inside the cable and leakage is low. Twisted pair cancels the field by twisting two conductors together, which makes it cheap and flexible but dependent on balance: a crushed or untwisted section radiates and picks up noise.
| Cable | Impedance | Usable bandwidth | Practical run |
|---|
| RG-6 | 75 ohm | 1 GHz | 60 m (200 ft) |
| RG-59 | 75 ohm | 500 MHz | 30 m (100 ft) |
| RG-11 | 75 ohm | 1 GHz | 120 m (400 ft) |
| Cat 5e | 100 ohm | 100 MHz | 100 m (330 ft) |
| Cat 6 | 100 ohm | 250 MHz | 100 m, 10G to 55 m |
Where coax still wins
Satellite and aerial feeds need the 75 ohm impedance and the DC path for a switch or a preamplifier, and no twisted pair product replaces that. Analogue cameras and older intercoms also work on coax with no converter. Where a building already has a coaxial cable white jacket run to each room, reusing it for MoCA avoids pulling new cable through finished walls.
Bandwidth and distance in practice
RG-6 at 1 GHz
Loss rises with the square root of frequency, so RG-6 measures about 5 dB per 30 metres at 500 MHz and 18 dB per 100 metres at 1 GHz. A 60 metre run with a splitter costs 11 dB plus 4 dB, which leaves little margin for a weak signal; use RG-11 beyond that.
Cat 6 at 250 MHz
Insertion loss at 250 MHz is about 20 dB over 100 metres, and the limit is not loss alone but crosstalk between the four pairs. That is why twisted pair stops at 100 metres for a channel while a coax feed can run further at lower frequency.
Power, shielding and earthing
Earthing a coax shield
Bond the screen at the entry point to the building earthing system, and never leave a shield floating at both ends of a long run, which turns it into an aerial for common mode noise. A splitter housing that is not bonded will pass hum into every outlet.
Power over twisted pair
PoE delivers 12.95 W to 71 W at the device over the same pairs that carry data, which coax cannot do without a separate injector and a bias tee. That single fact decides most new camera and access point installations.
Reusing an existing coax run
A coaxial cable tv to hdmi converter turns an analogue feed into HDMI at the display, but it does not turn coax into a network. For data over the old cable, use MoCA adapters in pairs, which give about 1 Gbit/s shared per segment and need a splitter rated to 1.6 GHz. Where only a line level audio feed is needed, a coaxial output cable from a digital source carries 192 kHz S/PDIF over 75 ohm, and the impedance match matters more than the length.
Practical scenarios
- Situation: a warehouse adding twelve IP cameras to an existing analogue coax system – run Cat 6 for the new drops; the old coax stays for the four legacy cameras on their own recorder.
- Situation: a 90 metre (295 ft) aerial drop down a tower – RG-11 rather than RG-6, because 1 GHz loss at that length removes the margin a splitter needs.
- Situation: a classroom with one coax outlet and a new projector – a coax to HDMI converter at the wall, not a balun, because the source is already modulated.
- Situation: a retrofit where pulling cable is impossible – MoCA adapters on the existing coax give a shared gigabit, but never feed PoE through it.
FAQ
Can coax be used for Ethernet?
Only through MoCA or a media converter pair, never directly. The impedance and the signalling scheme differ, so a passive adapter between the two will not pass an Ethernet link.
Which is better for a long outdoor run?
Coax survives distance and moisture better on a single feed, while fibre beats both for data. If the far end needs power and data, twisted pair with a mid-span switch is usually the cheapest answer.
Why does a coax splitter degrade the picture?
Each two way split costs about 3.5 dB to 4 dB, and an unmatched port reflects signal back down the line. Terminate unused ports with a 75 ohm cap and keep the number of splits to two.
