Quick answer: Flat coaxial cable is a 75 ohm cable pressed into a ribbon a millimetre thick so it can pass under a door or through a window frame. The geometry costs performance: attenuation is roughly 60 to 100 percent higher than RG6 at the same length, shield coverage is usually foil only, and the impedance is less consistent along the run. It is fine for a 3 to 5 m feed to a television or a set-top box, and a poor choice for satellite, MoCA or cable modem links where the upstream band and the return loss both matter.
The product exists for one reason: a landlord, a listed building or a rented flat where drilling is not allowed. Used for that purpose over a short distance it works. Used as a substitute for a proper drop over 20 m, it produces exactly the symptoms of a weak signal, which then get blamed on the provider.
Why the flat profile exists
Doors, windows and skirting
A round RG6 cable is about 6.8 mm in diameter and will not pass a closed door or a sealed window without crushing. A flat ribbon of 0.5 to 1 mm thickness passes under a carpet edge, through a window seal or behind skirting, which is often the only route available without structural work.
The construction compromise
To keep the profile thin, the centre conductor becomes a flat strip rather than a round wire, the dielectric is a thin solid layer, and the shield is usually aluminium foil with a drain wire instead of a braid. That reduces coverage from about 95 percent to something closer to 100 percent foil with poor mechanical strength, and it makes the cable intolerant of repeated bending.
What the geometry costs
| Frequency | Flat coax, per 10 m | RG6, per 10 m | RG59, per 10 m |
|---|
| 100 MHz | About 2.4 dB | About 1.1 dB | About 1.7 dB |
| 500 MHz | About 5.5 dB | About 2.4 dB | About 3.7 dB |
| 1 GHz | About 8 dB | About 3.3 dB | About 5.2 dB |
| Shield coverage | Foil, foil plus drain | Foil plus braid | Braid, 95 percent |
Figures are typical for the class and vary between products. The point is the ratio: at 1 GHz a flat cable loses more than twice what RG6 loses over the same distance, and satellite intermediate frequencies sit in that band.
Where it is acceptable
Short feeds to a television
A terrestrial aerial feed to a single television over 3 to 5 m has margin to spare, because the signal at the wall plate is designed to be several dB above the receiver’s minimum. A flat cable in that position is a reasonable compromise, provided the connectors are properly fitted and the ribbon is not pinched in a door hinge.
Where the return path matters
Cable modems, satellite receivers and MoCA adapters all use the return path, and return loss is as important as attenuation. A flat cable with inconsistent impedance reflects energy back toward the source, which a modem sees as noise on the upstream channel. If the modem’s upstream power rises by several dB after fitting a flat cable, that is the cause.
Handling and connectors
Flat cable cannot be crimped with a standard F connector without a dedicated die, and the foil shield is easily creased where the connector clamps. Use compression fittings designed for the ribbon type, keep the bend radius generous, and never fold the cable back on itself to shorten it: a crease changes the impedance permanently. If the run must pass a window, fit a purpose-made flat window cable with moulded ends rather than a bare ribbon.
For anything permanent, replace it with round cable at the first opportunity. The RG6 cables overview covers the standard drop, the coaxial connectors and adapters page covers the fittings, and the 75 ohm RG6 coax reference explains why the impedance, not the copper, sets the ceiling.
Weatherproofing and mechanical limits
A flat cable crossing a window is exposed to repeated compression every time the window closes, and the foil shield creases at that point. Fit a purpose-made window cable with a moulded flat section and keep the transition outside the frame, not in the hinge. Outdoors, even for a short run, use a UV-rated jacket and seal the connector with self-amalgamating tape. Water ingress at an F connector raises loss and introduces noise long before the cable itself fails, and the fault usually appears weeks later in wet weather.
Practical scenarios
- Rented flat with an aerial point in the hall: a 4 m flat feed under the door to the television is a sensible temporary solution; label it so the next tenant knows what it is.
- Cable modem that keeps dropping: replace the flat window feed first, because upstream power and error rates are the first things to suffer.
- Satellite receiver in a listed building: use a flat window cable rated for the intermediate frequency band, and keep it as short as physically possible.
- Motorhome or caravan: a flat entry cable through a window seal works well, but disconnect it before moving; repeated flexing breaks the foil.
FAQ
Is flat coaxial cable as good as RG6?
No. It loses roughly twice as much signal at 1 GHz, has a weaker shield and less consistent impedance. For a short feed it makes no practical difference; for satellite, MoCA or a cable modem it can be the difference between a stable link and daily dropouts.
Can flat coax be used outdoors?
Only if it is explicitly rated for outdoor use. Most flat cable has a PVC jacket and a foil shield that degrades in ultraviolet light and water. A window feed that crosses outside, even briefly, needs a UV-rated jacket or a proper round drop to a wall entry.
Will it reduce my internet speed?
It can reduce stability rather than headline speed. Higher loss lowers the signal-to-noise ratio on the downstream channels and raises upstream transmit power, which shows up as dropped connections or slower speeds at peak times rather than a permanently lower rate.
