diff --git a/libm65/cgen65.f90 b/libm65/cgen65.f90
index bfdd210a6..001ff1840 100644
--- a/libm65/cgen65.f90
+++ b/libm65/cgen65.f90
@@ -44,7 +44,7 @@ subroutine cgen65(message,mode65,nfast,samfac,nsendingsh,msgsent,cwave,nwave)
      tsymbol=4096.d0/(nfast*11025.d0)    !Time per symbol
   else
      nsendingsh=1                        !Flag for shorthand message
-     nsym=32
+     nsym=32/nfast
      tsymbol=16384.d0/11025.d0
   endif
 
diff --git a/libm65/mapsim.f90 b/libm65/mapsim.f90
index 547bbed4c..f01a8a3af 100644
--- a/libm65/mapsim.f90
+++ b/libm65/mapsim.f90
@@ -87,7 +87,8 @@ program mapsim
         if(npol.lt.0) pol=(isig-1)*180.0/nsigs
         a=cos(pol/rad)
         b=sin(pol/rad)
-        f=1000.0*(f1 + (isig-1)*(f2-f1)/(nsigs-1.0))
+        f=1000.0*(f1+f2)/2.0
+        if(nsigs.gt.1) f=1000.0*(f1 + (isig-1)*(f2-f1)/(nsigs-1.0))
         dphi=twopi*f*dt + 0.5*twopi
 
         snrdbx=snrdb