Splitter :
PCB must be mounted into a screening METAL enclosure (absolutely needed for maximal noise suppression).
BNC antenna input 50 Ohms coax. See "Pin1 problems". Connected in good contact with the outside of the enclosure.
BNC receiver output 50 Ohms coax. Connected in good contact with the outside of the enclosure.
BNC power input 12.5Vdc - 16Vdc @ 150mA. Internal filtered + CMC. Connected in good contact with the outside of the enclosure.
Power input is protected against over-voltage, wrong polarity and short circuits. 
The power connection cable should be screened. See : "De-noising the external powersupply."