diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9bce7d3a3..c05e4072b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -842,6 +842,9 @@ if (WIN32)
   qt5_use_modules (wsjt_qt AxContainer AxBase)
 endif (WIN32)
 
+add_executable (jt4sim lib/jt4sim.f90 wsjtx.rc)
+target_link_libraries (jt4sim wsjt_fort wsjt_cxx)
+
 add_executable (jt9sim lib/jt9sim.f90 wsjtx.rc)
 target_link_libraries (jt9sim wsjt_fort wsjt_cxx)
 
@@ -962,7 +965,7 @@ install (TARGETS wsjtx
   BUNDLE DESTINATION . COMPONENT runtime
   )
 
-install (TARGETS jt9 jt65code jt9code jt4code wsprd message_aggregator 
+install (TARGETS jt9 jt65code jt9code jt4code jt4sim wsprd message_aggregator 
   RUNTIME DESTINATION ${WSJT_BIN_DESTINATION} COMPONENT runtime
   BUNDLE DESTINATION ${WSJT_BIN_DESTINATION} COMPONENT runtime
   )
diff --git a/lib/jt4sim.f90 b/lib/jt4sim.f90
new file mode 100644
index 000000000..d706cf74f
--- /dev/null
+++ b/lib/jt4sim.f90
@@ -0,0 +1,117 @@
+program jt4sim
+
+! Generate simulated data for testing the JT4 decoder
+
+  use wavhdr
+  use packjt
+  use jt4
+  parameter (NMAX=60*12000)
+  type(hdr) h
+  integer*2 iwave(NMAX)                  !Generated waveform
+  real*4 dat(NMAX)
+  real*4 r(2)
+  real*8 f0,f,dt,twopi,phi,dphi0,dphi,baud,fspread,fsample,freq,sps
+  character message*22,msgsent*22,arg*8,fname*11,submode*1
+
+  integer*4 itone(206)             !Channel symbols (values 0-8)
+
+  nargs=iargc()
+  if(nargs.ne.5) then
+     print*,'Usage:   jt4sim "message"       [A-G] fspread SNR nfiles'
+     print*,'Example: jt4sim "CQ K1ABC FN42"   F     200   -17   1'
+     go to 999
+  endif
+
+  call getarg(1,message)  
+  call fmtmsg(message,iz)
+  call getarg(2,arg)
+  read(arg,*) submode
+  mode4=ichar(submode) - ichar('A') + 1
+  call getarg(3,arg)
+  read(arg,*) fspread                !Frequency spread (Hz)
+  call getarg(4,arg)
+  read(arg,*) snrdb                  !S/N in dB (2500 hz reference BW)
+  call getarg(5,arg)
+  read(arg,*) nfiles                 !Number of files     
+
+  rmsdb=25.
+  rms=10.0**(0.05*rmsdb)
+  fsample=12000.d0                   !Sample rate (Hz)
+  dt=1.d0/fsample                    !Sample interval (s)
+  twopi=8.d0*atan(1.d0)
+  npts=60*12000
+  sps=12000.d0/4.375d0               !2742.857...
+  f0=1000.d0                         !Frequency of lowest tone (Hz)
+
+  h=default_header(12000,npts)  
+
+  if(message(1:3).eq.'sin') read(message(4:),*) sinfreq
+  
+  write(*,1000)
+1000 format('File  S/N  Message'/    &
+            '--------------------------------')
+
+  call gen4(message,0,msgsent,itone,itype) !Encode message into tone #s
+!  write(*,1030) itone
+!1030 format(/'Channel symbols'/(30i2))
+
+
+  do ifile=1,nfiles                            !Loop over all files
+     nmin=(ifile-1)*2
+     ihr=nmin/60
+     imin=mod(nmin,60)
+     write(fname,1002) ihr,imin                !Create output filename
+1002 format('000000_',2i2.2)
+     open(10,file=fname//'.wav',access='stream',status='unknown')
+
+     if(snrdb.lt.90) then
+        do i=1,npts
+           dat(i)=gran()
+        enddo
+     else
+        dat(1:npts)=0.
+     endif
+
+     snrdbx=snrdb 
+     sig=10.0**(0.05*snrdbx)
+     if(snrdb.gt.90.0) sig=1.0
+     write(*,1020) ifile,snrdbx,msgsent
+1020 format(i3,f7.1,2x,a22)
+
+     phi=0.
+     baud=12000.d0/sps
+     isym0=0
+     k0=12000
+     do k=k0+1,npts
+        isym=1.d0 + (k-k0)/sps
+        if(isym.gt.206) exit
+        if(isym.ne.isym0) then
+           freq=f0 + itone(isym)*baud*nch(mode4)
+           if(message(1:3).eq.'sin') freq=sinfreq
+           dphi0=twopi*freq*dt
+           dphi=dphi0
+           isym0=isym
+        endif
+
+        if(fspread.gt.0.d0 .and. mod(k,120).eq.0) then
+           call random_number(r)
+           f=freq + 0.5*fspread*(r(1)+r(2)-1.0)
+           dphi=twopi*f*dt
+        endif
+
+        phi=phi + dphi
+        if(phi.gt.twopi) phi=phi-twopi
+        xphi=phi
+        dat(k)=dat(k) + sig*sin(xphi)
+     enddo
+
+     fac=32767.0
+     if(snrdb.ge.90.0) iwave(1:npts)=nint(fac*dat(1:npts))
+     if(snrdb.lt.90.0) iwave(1:npts)=nint(rms*dat(1:npts))
+     
+     write(10) h,iwave(1:npts)
+     close(10)
+
+  enddo
+
+999 end program jt4sim