A Bias Tee is used in base stations with Tower Mounted Amplifiers (TMA). A Bias Tee injects the DC current into an existing RF cable for biasing the TMA. A Bias Tee has DC, BTS and antenna ports. The DC signal is transferred to the antenna port, but not to the BTS port. The RF signal from either BTS or antenna ports does not enter the DC port. SDP Bias Tee presents extremely low RF insertion loss between the BTS and antenna ports and very high RF isolation between the DC port and BTS/antenna ports. There is also high DC isolation between the DC port and BTS port. The unit protects the BTS from static discharge and lightning.