Gang, Have a 75A-3 in nice condition, looking for a narrower mechanical filter. Possible line on an "F" filter which I have been told will fit the beast. Number: F455F-15, 526-9227-00. Should be 1.5 kHz - will it fit the 75A-3? Alternatively, anyone out there got a F455B-08, 596-2923-002 they want to get rid of? Thanks in advance, 73, Al N5AIT