Have this interesting Noise Filter Unit that is surplus to my needs.  Tested to be operational

The JPS NIR-10 audio filter allows reception of difficult to read signals and reduces listener fatigue. Operates on radio receiver audio outputs then provides its own volume-adjustable processed audio to an external 3 to 8 ohm speaker (not supplied). The NIR-10 reduces or eliminates white/pink noise, ignition noise, static interference, RTTY interference, and power line noise. PEAK function reduces white noise interference. The Notch Filter mode removes multiple heterodynes and acts in 3 milliseconds. Band Pass mode has continuously adjustable center frequency, selectable bandwidths (0.25, 0.6 and 1 kHz), vertical-skirted filters, and greater than 60 dB ultimate rejection. The rear panel has RCA phono jacks for:  Audio Input, Speaker Output, Remote Bypass, Inv Rem Bypass. There is also a jack for 12 VDC Input (1 Amp). The front panel features a 1/4 inch headphone jack. 7 x 2 x 7 inches.