SUBROUTINE HT_4d(dl_v,ZTRA3,STRA3) 6,1

      IMPLICIT NONE
      include 'champ.cdk'
      include 'chobs.cdk'

      COMPLEX ZTRA3(IKTX,IKTY,52),STRA3(IKTX,IKTY,52)
      COMPLEX Z(IKTX,IKTY),S(IKTX,IKTY)
      REAL U(N,N),W(N,N)
      REAL dl_v(2*N*N*(NSTOP+2)),dl_u(2*N*N)
      INTEGER IR, NOBS 
      INTEGER KX,KY,KW
      REAL JX

      NOBS = 0
      DO NT = 1, NSTOP+2
        DO IR = 1, 2*N*N
           NOBS     = NOBS+1
           dl_u(IR) = dl_v(NOBS)
        END DO
        CALL HT(dl_u,Z,S,NT)
        DO KX = 1,IKTX
        DO KY = 1,IKTY
           ZTRA3(KX,KY,NT) = Z(KX,KY)
           STRA3(KX,KY,NT) = (0.,0.)
        END DO 
        END DO
       END DO

      RETURN
      END