An electrical filter includes a circuit board with an insulative substrate of alternating wide and narrow portions between input and output ends. Capacitors received in through-holes in the wide portions are electrically coupled to signal traces on a signal surface and ground traces on a ground surface of the circuit board. Conductive coils about narrow portions may form inductors, electrically coupled between the signal traces and an input and/or output. The circuit board, capacitors and inductors may be positioned in a first enclosure, (e.g., tube), with sealed electrical connections to an exterior. The first enclosure may be positioned in a second enclosure (e.g., tube). The filter may also include a high frequency dissipation filter section employing a metal powder filter, with metal powder and epoxy. Non-magnetic and/or superconducting materials may be employed.