ulkojohtin

Ulkojohtin is a term used in Finnish electrical engineering to denote the outer conductor of a shielded or coaxial cable system. It refers to the conductive layer that surrounds the inner conductor, providing electromagnetic shielding, a return path for current, and a ground reference in many installations. The concept is central to maintaining signal integrity in RF and high-frequency applications.

In construction, ulkojohtin can be realized as a metal foil, a braided wire shield, or a combination of foil and braid. Materials typically used include copper, tin-plated copper, or aluminum, chosen for conductivity, mechanical flexibility, and corrosion resistance. Shields may be single-layer or multi-layer, and they are designed to minimize leakage and parasitic inductance while maintaining impedance.

The primary functions of the outer conductor are shielding and grounding. By surrounding the inner conductor, the ulkojohtin suppresses external electromagnetic interference and reduces radiation from the cable itself. It also provides a return path for currents and helps stabilize the characteristic impedance of the line. The integrity of the outer conductor is essential; damage, corrosion, or discontinuities can degrade shielding effectiveness and increase susceptibility to interference.

Common applications include coaxial cables for radio frequency transmission, shielded data and video cables, and certain shielded power cables. Proper termination and continuity testing of the outer conductor are important during installation and maintenance to ensure reliable performance.

See also: Shield, Faraday cage, Coaxial cable, Ground.