Fix an off-by-one error. Remove attempt to refine DT estimate using polynomial interpolation.

lib/ft8/ft8_downsample.f90

@@ -5,15 +5,23 @@ subroutine ft8_downsample(dd,newdat,f0,c1)
   parameter (NMAX=15*12000,NSPS=1920)
   parameter (NFFT1=192000,NFFT2=3200)      !192000/60 = 3200
   
-  logical newdat
+  logical newdat,first
   complex c1(0:NFFT2-1)
   complex cx(0:NFFT1/2)
-  real dd(NMAX),x(NFFT1)
+  real dd(NMAX),x(NFFT1),taper(0:100)
   equivalence (x,cx)
-  save cx
+  data first/.true./
+  save cx,first,taper
 
+  if(first) then
+     pi=4.0*atan(1.0)
+     do i=0,100
+       taper(i)=0.5*(1.0+cos(i*pi/100))
+     enddo
+     first=.false.
+  endif
   if(newdat) then
-! Data in dd have changed, recompute the long FFT     
+! Data in dd have changed, recompute the long FFT
      x(1:NMAX)=dd
      x(NMAX+1:NFFT1)=0.                       !Zero-pad the x array
      call four2a(cx,NFFT1,1,-1,0)             !r2c FFT to freq domain
@@ -23,9 +31,9 @@ subroutine ft8_downsample(dd,newdat,f0,c1)
   df=12000.0/NFFT1
   baud=12000.0/NSPS
   i0=nint(f0/df)
-  ft=f0+8.0*baud
+  ft=f0+8.5*baud
   it=min(nint(ft/df),NFFT1/2)
-  fb=f0-1.0*baud
+  fb=f0-1.5*baud
   ib=max(1,nint(fb/df))
   k=0
   c1=0.
@@ -33,6 +41,8 @@ subroutine ft8_downsample(dd,newdat,f0,c1)
    c1(k)=cx(i)
    k=k+1
   enddo
+  c1(0:100)=c1(0:100)*taper(100:0:-1)
+  c1(k-1-100:k-1)=c1(k-1-100:k-1)*taper
   c1=cshift(c1,i0-ib)
   call four2a(c1,NFFT2,1,1,1)            !c2c FFT back to time domain
   fac=1.0/sqrt(float(NFFT1)*NFFT2)

lib/ft8/ft8b_2.f90

@@ -131,7 +131,6 @@ subroutine ft8b_2(dd0,newdat,nQSOProgress,nfqso,nftx,ndepth,lapon,lapcqonly,   &
   call twkfreq1(cd0,NP2,fs2,a,cd0)
   xdt=xdt2
   f1=f1+delfbest                           !Improved estimate of DF
-
   call sync8d(cd0,i0,ctwk,0,2,sync)
 
   do k=1,NN
@@ -323,14 +322,7 @@ subroutine ft8b_2(dd0,newdat,nQSOProgress,nfqso,nftx,ndepth,lapon,lapcqonly,   &
      call extractmessage77(message77,message)
 ! This needs fixing for messages with i5bit=1        
      call genft8_174_91(message,mygrid6,bcontest,i5bit,msgsent,msgbits,itone)
-     if(lsubtract) then
-       call sync8d(cd0,i0-1,ctwk,0,2,sm1)
-       call sync8d(cd0,i0,ctwk,0,2,sp0)
-       call sync8d(cd0,i0+1,ctwk,0,2,sp1)
-       pk=0.5*(sm1-sp1)/(sp1-2*sp0+sm1)
-       xdti=(i0+pk)*dt2
-       call subtractft8(dd0,itone,f1,xdti)
-     endif
+     if(lsubtract) call subtractft8(dd0,itone,f1,xdt) 
      xsig=0.0
      xnoi=0.0
      do i=1,79

lib/ft8/ft8sim.f90

@@ -142,15 +142,15 @@ program ft8sim
               call genft8_174_91(msg,mygrid6,bcontest,i3bit,msgsent,msgbits,itone)
            endif
         endif
-!        k=-1 + nint((xdt+0.5+0.01*gran())/dt)
-        k=-1 + nint((xdt+0.5)/dt)
-        ia=k+1
+!        k=nint((xdt+0.5+0.01*gran())/dt)
+        k=nint((xdt+0.5)/dt)
+        ia=k
         phi=0.0
         do j=1,NN                             !Generate complex waveform
            dphi=twopi*(f0*dt+itone(j)/real(NSPS))
            do i=1,NSPS
-              k=k+1
               if(k.ge.0 .and. k.lt.NMAX) c0(k)=cmplx(cos(phi),sin(phi))
+              k=k+1
               phi=mod(phi+dphi,twopi)
            enddo
         enddo