diff --git a/CMakeLists.txt b/CMakeLists.txt
index e1ccf1389..2c196cbb2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1295,6 +1295,9 @@ target_link_libraries (jt4sim wsjt_fort wsjt_cxx)
 add_executable (jt65sim lib/jt65sim.f90 wsjtx.rc)
 target_link_libraries (jt65sim wsjt_fort wsjt_cxx)
 
+add_executable (sumsim lib/sumsim.f90 wsjtx.rc)
+target_link_libraries (sumsim wsjt_fort wsjt_cxx)
+
 add_executable (qra64sim lib/qra/qra64/qra64sim.f90 wsjtx.rc)
 target_link_libraries (qra64sim wsjt_fort wsjt_cxx)
 
diff --git a/lib/sumsim.f90 b/lib/sumsim.f90
new file mode 100644
index 000000000..e05f8d4d0
--- /dev/null
+++ b/lib/sumsim.f90
@@ -0,0 +1,41 @@
+program sumsim
+
+! Sum a number of *.wav files so that multiple signals are present
+
+  use wavhdr
+  parameter (NMAX=60*12000)
+  type(hdr) h                            !Header for the .wav file
+  integer*2 iwave(NMAX)                  !i*2 data
+  real wave(NMAX)                        !r*4 data
+  character*80 fname
+
+  nargs=iargc()
+  if(nargs.lt.1) then
+     print*,'Usage:    sumsim file1 [file2, ...]'
+     go to 999
+  endif
+  wave=0.
+
+  do ifile=1,nargs
+     call getarg(ifile,fname)
+     open(10,file=trim(fname),status='old',access='stream')
+     read(10) h
+     npts=h%ndata/2
+     nfsample=h%nsamrate
+     read(10) iwave(1:npts)
+     n=len(trim(fname))
+     wave(1:npts)=wave(1:npts)+iwave(1:npts)
+     rms=sqrt(dot_product(wave(1:npts),wave(1:npts))/npts)
+     write(*,1000) ifile,npts,float(npts)/nfsample,rms,fname(n-14:n)
+1000 format(i3,i8,f6.1,f10.3,2x,a15)
+     close(10)
+  enddo
+
+  fac=1.0/sqrt(float(nargs))
+  iwave(1:npts)=nint(fac*wave(1:npts))
+  
+  open(12,file='000000_0000.wav',access='stream',status='unknown')
+  write(12) h,iwave(1:npts)
+  close(12)
+
+999 end program sumsim