📘 05-01: Copper Cabling¶
📌 Twisted-Pair Basics¶
Most LAN copper cabling is twisted pair — pairs of wires twisted together to cancel EMI and crosstalk (common-mode rejection).
| Type | Shielding |
|---|---|
| UTP (Unshielded Twisted Pair) | None — most common |
| STP (Shielded Twisted Pair) | Foil/braid — for noisy environments (needs grounding) |
Connector: RJ-45 (8P8C).
📌 Category Ratings¶
| Category | Max speed | Max distance | Notes |
|---|---|---|---|
| Cat 3 | 10 Mbps | 100 m | Legacy/phone |
| Cat 5 | 100 Mbps | 100 m | Obsolete |
| Cat 5e | 1 Gbps | 100 m | Common baseline |
| Cat 6 | 10 Gbps (to ~55 m) / 1 Gbps to 100 m | 100 m | |
| Cat 6a | 10 Gbps | 100 m | Modern 10G choice |
| Cat 7 / 8 | 10–40 Gbps | 100 m / 30 m | Shielded, data-center |
Horizontal copper is limited to 100 m regardless of category.
📌 Common Problems¶
| Problem | Cause |
|---|---|
| Attenuation | Signal weakens over distance |
| Crosstalk (NEXT/FEXT) | One pair's signal bleeds into another |
| EMI/RFI | Interference from motors, lights, power lines |
Mitigate EMI with STP or fiber, and route away from noise sources.
📌 Coaxial¶
Coax (RG-6, RG-59) is used for cable TV/broadband (DOCSIS) and legacy Ethernet. Connectors: F-type, BNC.
Tip
Key idea — Twisting cancels interference. Use Cat 5e for 1G and Cat 6a for 10G, all capped at 100 m. Fight EMI with shielding or fiber.
See also: Fiber-Optic Cabling, Cable Issues, Tools & PoE
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