A dual operation mode all temperature filter is provided. The dual
operation mode filter is provided with a housing defining at least two
cavities, an input port and an output port. It is also provided with a
non-superconducting resonator disposed in a first one of the cavities and
a superconducting resonator disposed in a second one of the cavities. The
second resonator comprises a superconducting material containing 8-15%
silver. The dual operation mode filter filters at a relatively high level
at temperatures below a threshold temperature and at a lower,
conventional level, at temperatures below the threshold.