HDBaseT & extenders
Sending video, power and control over category cable.
HDMI was designed to connect a player to a TV a few metres away. Commercial rooms are bigger than that: the rack is in a cupboard, the projector is on the ceiling, the floor box is under the table. The higher the data rate, the shorter a plain HDMI cable can reliably run. Beyond that, the signal needs an extender.
How an extender works
An extender is a pair of boxes. The transmitter (TX) takes HDMI in at the source end and converts it into a form that travels well over a long cable. The receiver (RX) at the far end turns it back into HDMI for the display. Many switchers have extender outputs built in, and many projectors and displays have a built-in receiver input, so one or both boxes may disappear into other equipment.
HDBaseT
The most common copper extension technology in commercial AV is HDBaseT, a standard promoted by the HDBaseT Alliance. It sends uncompressed video over a single category (Cat) cable for up to 100 m, and can carry several other things along with it. The Alliance markets this as “5Play”:
| Carried | What it means in a room |
|---|---|
| Video | Uncompressed HD and 4K video, with HDCP |
| Audio | The audio embedded in the HDMI signal |
| Ethernet | A network connection for the far-end device, such as a projector's control port |
| Control | RS-232 and IR, so the rack can control the display at the other end |
| Power | Power over HDBaseT (PoH): one end can power the other, so only one box needs a power outlet |
- Video
- Uncompressed HD and 4K video, with HDCP
- Audio
- The audio embedded in the HDMI signal
- Ethernet
- A network connection for the far-end device, such as a projector's control port
- Control
- RS-232 and IR, so the rack can control the display at the other end
- Power
- Power over HDBaseT (PoH): one end can power the other, so only one box needs a power outlet
Not every product supports every feature — many extenders omit Ethernet, or power only in one direction — so compare the spec sheets of both ends.
Bandwidth and 4K
HDBaseT carries video uncompressed up to roughly the bandwidth of HDMI 1.4. That covers 1080p and many 4K formats such as 4K30 or 4K60 at 4:2:0. The highest-bandwidth HDMI 2.0 formats — 4K60 at 4:4:4, or HDR at high bit depths — don't fit as-is. Products that carry them over HDBaseT apply light compression, usually marketed as visually lossless. Check the spec sheet before promising a format (Chapter 2's bandwidth lesson shows why the numbers matter).
It looks like Ethernet, but it isn't
HDBaseT uses the same cable and RJ45 connectors as a computer network, which leads to one of the most common installation mistakes. The signal is not Ethernet: it can't pass through a network switch, and it needs a continuous copper link from transmitter to receiver. Good practice for the cable itself:
- Use solid-core cable of the category the manufacturer specifies — often Cat6 or better, frequently shielded for 4K.
- Terminate both ends the same way (T568A or T568B), with shielded connectors if the cable is shielded.
- Avoid extra joins. Patch panels, wall plates and couplers each add loss; follow the manufacturer's rules on what's allowed.
- Keep away from power cables, and cross them at right angles where the routes meet.
- Test the finished link with a cable certifier, or at least the link-quality readout many extenders provide.
Should work
- ✓Signal. 4K60 4:2:0 fits within HDBaseT's uncompressed bandwidth.
- ✓Distance. 60 m is within typical ratings for this signal.
- ✓Cable. Solid-core cable suitable for this run; check the manufacturer's minimum category.
- ✓Path. One continuous run, terminated the same way (T568A or T568B) at both ends.
- ✓Interference. Kept away from power cabling.
A teaching checklist based on general HDBaseT practice, not a guarantee. Ratings and cable requirements vary by product — the manufacturer's installation guide always wins.
Other ways to go the distance
| Method | Strength | Watch out for |
|---|---|---|
| Active HDMI cable | No boxes; some are optical fibre inside | Usually works in one direction only; fixed length |
| HDBaseT | Video, control and power on one cable to 100 m | Point-to-point copper; bandwidth limit for top 4K formats |
| Fibre extender | Far longer distances; immune to electrical interference | Fibre termination skills and cost |
| AV-over-IP | Routes over a network switch to any number of endpoints | Network design — Chapters 8 and 9 |
- Active HDMI cable
- StrengthNo boxes; some are optical fibre inside
- Watch out forUsually works in one direction only; fixed length
- HDBaseT
- StrengthVideo, control and power on one cable to 100 m
- Watch out forPoint-to-point copper; bandwidth limit for top 4K formats
- Fibre extender
- StrengthFar longer distances; immune to electrical interference
- Watch out forFibre termination skills and cost
- AV-over-IP
- StrengthRoutes over a network switch to any number of endpoints
- Watch out forNetwork design — Chapters 8 and 9
Key takeaways
- 01Long HDMI runs fail; an extender pair converts the signal for a long cable and back again.
- 02HDBaseT sends uncompressed video, audio, Ethernet, control and power over one Cat cable up to 100 m.
- 03The highest-bandwidth 4K formats need light compression to travel over HDBaseT — check spec sheets.
- 04HDBaseT is not Ethernet: it can't pass through a network switch and needs a continuous copper link.
- 05Use solid-core cable of the specified category, consistent termination, few joins, and test the link.
Check your understanding
Q1An installer routes an HDBaseT extender through the building's network switch. What happens?
Q2What is the standard maximum HDBaseT cable length?
Q3The HDBaseT receiver behind a wall display has no spare power outlet. Which feature helps?