L1 GPS Filter (Pass DC) The L1FPDC is a one input, one output RF device that provides additional GPS L1 filtering from a GPS Antenna. The frequency response covers L1 centered at 1575MHz. In the normal configuration, the RF output (J1) passes DC from the connected GPS receiver through the input port to the antenna, allowing the GPS receiver to power the antenna. All filters are available with N-type, SMA, BNC or TNC connectors.   L1/L2 GPS Filter (Pass DC) The L1L2FPDC is a GPS passband filter designed specifically for the GPS L1 and L2 carrier frequencies. The L1L2FPDC lowers the out of band noise and interference by 20dB. The DC voltage is then passed to the intended GPS antenna or source. All filters are available with N-type, SMA, BNC or TNC connectors.