[Collins] R-390A Filters

[solo22@sbcglobal.net]

A very nice gentleman supplied me with a 2kc and 4kc filters.  Although 
I'm basically cw oriented for this unit,  I think  I'd still like an 8kc 
R-390A filter.   Anyone have one at a reasonable price?   Also I'm told 
the R-390A used either an audio filter for cw or some kind of xtal 
filter for it's 500cps.  Can anyone elaborate on this?  This stuff is 
all going into a 75A4.  I'm too cheap to pay the going price for a 75A4 
500hz filter.  Has any of you boot strapped any other 500hz 455khz 
 crystal, ceramic, or machanical filter in one?   Thanks as usual.  73, Ron