How Cable Construction Affects Performance

Lay length and twist

In a twisted pair, the lay length controls crosstalk. Manufacturers vary the lay of each pair inside a cable so no two pairs stay parallel over any distance. Tight, well-controlled lay is why one CAT6 cable passes an alien crosstalk test and another does not.

In power cables, the lay of the cores affects the cable's flexibility, its bend radius and how evenly current is shared between parallel conductors.

Fillers, geometry and roundness

Fillers keep a multicore cable round. Roundness matters for gland sealing, armour bedding and the crush strength of the finished cable — an out-of-round cable seals poorly and armours unevenly.

In data cables, a cross-filler physically separates pairs and is one of the main tools for maintaining performance at higher frequencies.

Insulation material and wall thickness

Insulation determines the operating temperature and the dielectric behaviour. XLPE allows a 90 °C conductor temperature against PVC's 70 °C, which for the same size means meaningfully more current. Foamed polyethylene lowers capacitance in data and coaxial designs, improving high-frequency performance.