I have a VERY SIMILAR unit to what you are describing that I just very recently found in a drawer and it was in its original box with the instruction sheet. I don't know if I ever used it after I purchased it as it was still wrapped in the bubble wrap in the box when I found it.It is probably from the late 70's or later. Ultra wide band RF receiver pre-amp freq 25Mhz--1 Ghz part number BC 004 Uniden America Corp made in the Philippines. I bought it new but can't find the box. It took power from the scanner plug and plugged back in the scanner. Has a bypass switch and a BNC input jack and a short cable to plug into the scanner.