A muffler for coupling to an exhaust port of an internal combustion engine. A metric that is indicative of a reliability of the position fix may be generated based, at least in part, on a number of independent ones of the data items andor an indication of reliability of at least one of the data items. The high frequency filter further incorporates an opened or fully enclosed enclosure over the strip line or microstrip circuitry and may be manufactured on a relatively thick dielectric substrate having a thickness that is greater than about a twentieth of the filter’s band-pass wavelength in the dielectric substrate.