[TenTec] On Crystal Filters

[Kimberly Elmore]

In discussion of an Omni D, Rick and maybe someone else mentioned that old crystal filters may no longer meet spec and can result in significantly reduced sensitivity. I know that crystals age and that if they don't all age the same way the filter may drift out of spec, but this is the first I've heard that it could affect performance to such and extent.  Is this a characteristic of all crystal filters, or only those used in the Omni D series by TT? I'm curious because I have INRAD filters in an older radio. They seem to work as they did when I first installed them 20+ years ago and the radio seems as sensitive as it ever was. 

Kim N5OP