Twisted-pair Ethernet is the backbone of modern AV: it carries the network for AV-over-IP, the link for HDBaseT extenders, and power via PoE. Category (“Cat”) ratings define the cable’s bandwidth (MHz) and the speeds and distances it reliably supports. The universal rule: 100 m maximum channel length for standard Ethernet.
Categories at a glance
| Category | Bandwidth | Max speed | Distance at max speed | Typical use |
|---|---|---|---|---|
| Cat5e | 100 MHz | 1 Gbps | 100 m | Baseline gigabit, PoE |
| Cat6 | 250 MHz | 10 Gbps | 55 m (1G to 100 m) | Gigabit+, short 10G |
| Cat6a | 500 MHz | 10 Gbps | 100 m | 10G, high-power PoE |
| Cat7 | 600 MHz | 10 Gbps | 100 m | Shielded 10G (proprietary connectors) |
| Cat8 | 2000 MHz | 25/40 Gbps | 30 m | Data-center top-of-rack |
Cat6 does 10G only to ~55 m (and less with heavy alien crosstalk). For a full 100 m 10G run, use Cat6a. Cat7 uses non-RJ45 (GG45/TERA) connectors and is rarely specified for new AV work — Cat6a is the practical choice.
Shielding
- UTP (unshielded twisted pair) — most common; lighter, cheaper, easier to terminate.
- F/UTP, S/FTP (foil/braid shielded) — reject external noise and reduce crosstalk; needed in high-interference environments and to run 10G reliably in dense bundles. Shielded cable requires proper grounding at the patch panel or the shield can make noise worse.
PoE considerations
- Heat, not data, is the PoE limit. High-power PoE (Type 3/4, up to ~90 W) heats the conductors; bundled cables run hotter. Use larger-gauge conductors (23 AWG) and Cat6/6a for long high-power runs, and de-rate bundle sizes per the cable spec.
- Avoid CCA. Copper-clad aluminum has higher resistance — more voltage drop and heat. Use solid copper for any PoE run.
- Length reduces delivered power. Longer runs lose more to resistance; budget against the PoE Calculator using the device’s rated draw.
Practical notes
- Terminate to the right standard (T568B is the common default) and keep the twist as close to the connector as possible — untwisting degrades high-frequency performance.
- Solid core for permanent runs, stranded for patch leads. Solid handles distance better; stranded flexes without breaking.
- Test the channel. Certify long or high-speed runs with a cable tester, not just a continuity check — marginal cabling shows up as retrains and dropped AV streams.
Related
Sources
- ANSI/TIA-568.2 — balanced twisted-pair cabling components; defines Category 5e through Category 8.
- ISO/IEC 11801 — international generic cabling standard (Class D–I).
- IEEE 802.3 Ethernet Working Group — 802.3an (10GBASE-T) and 802.3bt (PoE) requirements over these cables.