diff --git a/lib/spec64.f90 b/lib/spec64.f90
new file mode 100644
index 000000000..b20c9507d
--- /dev/null
+++ b/lib/spec64.f90
@@ -0,0 +1,33 @@
+subroutine spec64(c0,npts2,jpk,s3a)
+
+  parameter (NSPS=2304)                      !Samples per symbol at 4000 Hz
+  complex c0(0:360000)                       !Complex spectrum of dd()
+  complex cs(0:NSPS-1)                       !Complex symbol spectrum
+  real s3a(0:63,1:63)                        !Synchronized symbol spectra
+
+  nfft4=221184
+  c0(npts2:)=0.
+  call four2a(c0,nfft4,1,-1,1)             !Forward c2c
+!  nsubmode=1
+!  ndown=16/nsubmode
+  ndown=16
+  nfft5=nfft4/ndown
+  npts3=npts2/ndown
+  call four2a(c0,nfft5,1,1,1)              !Inverse c2c, downsampled
+
+  nfft6=nsps/ndown
+  jpkd=nint(float(jpk)/ndown)
+  do j=1,63
+     jj=j+7                                !Skip first Costas array
+     if(j.ge.32) jj=j+14                   !Skip middle Costas array
+     ja=jpkd + (jj-1)*nfft6
+     jb=ja+nfft6-1
+     cs(0:nfft6-1)=1.3e-8*c0(ja:jb)
+     call four2a(cs,nfft6,1,-1,1)
+     do i=0,63
+        s3a(i,j)=real(cs(i))**2 + aimag(cs(i))**2
+     enddo
+  enddo
+
+  return
+end subroutine spec64