...under perpetual construction.
Here you can find the source code of the bpfilt program, for designing narrow-band bandpass filters. You can choose between the equiripple (Tchebyscheff), maximally flat (Butterworth) and minimum loss (Cohn) types.
The output is a netlist in APLAC or Spice (OPUS Spice) format.
Download the bpfilt source code.
Here is a design example of a filter for the LF band, centered at 137.7 kHz, with several types of coupling and matching.
Here is another design example, comparing the Cohn, Tchebyscheff and Butterworth filter types.