In radio stations the antenna cables are subject to long-term degradation or failure due to electrical, mechanical and environmental stress. To avoid severe damage, which may result in a breakdown of the station, a monitoring of the antenna cables and/or antennas is desired. A U- link connector is provided for simple refurbishment of the radio stations by simple exchanging existing U- link connectors. The U- link connector comprises a bias tee circuit, by which a DC signal can be coupled into the antenna cable for a cable test, which may even be performed during operation of an attached transmitter.