Does this do what you need?

SELECT A.LOCATN_K FROM TBL1 as A WHERE not exists (

select 1 from TBL2 as C where

C.LOCATN_K = A.LOCATN_K and

A.STRT_D < C.DATE and

(A.XCHG_OUT_D > C.DATE OR A.XCHG_OUT_D IS NULL)

) ;

If not, could you explain more clearly what is needed?