[1000mp] Sub Rcvr 500hz Filter Question

[frank60]

I just finished installing all the optional filters in a new Mark V.  
Everything seems to be working properly after I turned them all
on using the various menu options except for the Sub Rcvr.   

When I either turn on or off the sub receiver 500hz cw filter it
makes no difference in receive.    It stays broadbanded whether
the Menu 5-8 is On or OFF.   Did I miss something?   
I am assuming you can listen on the sub receiver and then use
the menu 5-8 to turn on and off the filter and hear the difference
in receive bandwidth?    

Anyone have any ideas?   Frank W7is  W7is@arrl.net