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.