diff --git a/src/dispersion.f90 b/src/dispersion.f90
index 85defcc..7cec6d0 100644
--- a/src/dispersion.f90
+++ b/src/dispersion.f90
@@ -3,9 +3,9 @@ module dispersion
   use calcei_mod
   implicit none
   integer, parameter :: dp=kind(1.0d0)
-  integer, parameter :: tmax=5,npts=500
+  integer, parameter :: npts=500
   real(dp), save :: ttv(npts+1),extv(npts+1)
-  real(dp), parameter :: dtex=2.0d0*tmax/dble(npts)
+  real(dp), parameter :: tmax=5.0d0,dtex=2.0d0*tmax/dble(npts)
 !
 contains
 !
@@ -21,16 +21,14 @@ subroutine colddisp(xg,yg,npl,nprf,sox)
   real(dp) :: nprf         ! N perpendicular to B (cold)
   real(dp) :: sox          ! sox=-1 ==> O mode, sox=1 ==> X mode
 !  
-  real(dp) :: yg2,npl2,nprf2,n_f2,dnl,del  
+  real(dp) :: yg2,npl2,dnl,del,dxg
 !  
   npl2=npl*npl
   dnl=1.0d0-npl2
+  dxg=1.0d0-xg
   yg2=yg*yg
-  del=sqrt(dnl*dnl+4.0d0*npl2*(1.0d0-xg)/yg2)
-  n_f2=1.0d0-xg-xg*yg2*(1.0d0+npl2+sox*del)/(1.0d0-xg-yg2)/2.0d0
-!
-  nprf2=n_f2-npl2                                                                                                        
-  nprf=sqrt(nprf2)
+  del=sqrt(dnl*dnl+4.0d0*npl2*dxg/yg2)
+  nprf=sqrt(dxg-npl2-xg*yg2*(1.0d0+npl2+sox*del)/(dxg-yg2)/2.0d0)
 !
 end subroutine colddisp
 !
@@ -403,7 +401,6 @@ subroutine diel_tens_fr(xg,yg,mu,npl,e330,cr,ci,epsl,lrm,fast)
 !
       llm=min(3,lrm)
 !
-      dt=2.0d0*tmax/dble(npts)
       bth2=2.0d0/mu
       bth=sqrt(bth2)
       mu2=mu*mu
@@ -417,7 +414,7 @@ subroutine diel_tens_fr(xg,yg,mu,npl,e330,cr,ci,epsl,lrm,fast)
         upl2=bth2*x**2
         upl=bth*x
         gx=1.0d0+t*t/mu
-        exdx=cr*extv(i)*gx/rxt*dt
+        exdx=cr*extv(i)*gx/rxt*dtex
 !
         n1=1
         if(fast.gt.2) n1=-llm