Unmanned Aerial Vehicles (UAVs) are limited by battery capacity, typically allowing less than 30 minutes of flight time. Tethered UAVs address this limitation by providing continuous power through a cable connected to a ground station, but require sophisticated tether management to prevent excessive slack or tension. This paper presents the design, implementation, and evaluation of a tension and length-controlled winch system for tethered UAVs. The system integrates a motorized winch with a guide mechanism for uniform winding, a load cell-based tension measurement system, angle sensor at the tether's base, and a catenary-based position estimation algorithm. Experimental results demonstrate that a PI controller successfully maintains tether tension at the 1.96N setpoint under both static and dynamic conditions. The position estimation system achieves average errors of 0.97m, 0.48m, and 0.6m in the x, y, and z directions respectively, comparable to similar approaches in literature. The complete system operates within a compact frame, powered by a 24V supply, and manages tether lengths up to 10m. This work provides a proof-of-concept for tether management systems that enable extended UAV flight times while maintaining stable operation and preventing unsafe tether conditions.