From d57b84be2768e9eadc9e40b0d8f6d13e72a022d6 Mon Sep 17 00:00:00 2001
From: Steven Franke <s.j.franke@icloud.com>
Date: Sun, 8 Mar 2020 12:03:52 -0500
Subject: [PATCH] More changes to increase ft8 decoder yield.

---
 lib/ft8/subtractft8.f90 | 11 ++++++++---
 lib/ft8/sync8.f90       | 10 ++++------
 lib/ft8_decode.f90      |  6 +++---
 3 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/lib/ft8/subtractft8.f90 b/lib/ft8/subtractft8.f90
index 1a374cc27..7c3b59082 100644
--- a/lib/ft8/subtractft8.f90
+++ b/lib/ft8/subtractft8.f90
@@ -8,10 +8,11 @@ subroutine subtractft8(dd0,itone,f0,dt,lrefinedt)
 ! Subtract         : dd(t)    = dd(t) - 2*REAL{cref*cfilt}
 
   parameter (NMAX=15*12000,NFRAME=1920*79)
-  parameter (NFFT=NMAX,NFILT=2800)
+  parameter (NFFT=NMAX,NFILT=4000)
   real dd(NMAX),dd0(NMAX)
   real window(-NFILT/2:NFILT/2)
   real x(NFFT+2)
+  real endcorrection(NFILT/2+1)
   complex cx(0:NFFT/2)
   complex cref,camp,cfilt,cw,z
   integer itone(79)
@@ -19,7 +20,7 @@ subroutine subtractft8(dd0,itone,f0,dt,lrefinedt)
   data first/.true./
   common/heap8/cref(NFRAME),camp(NMAX),cfilt(NMAX),cw(NMAX)
   equivalence (x,cx)
-  save first,/heap8/
+  save first,/heap8/,endcorrection
 
   if(first) then                         ! Create and normalize the filter
      pi=4.0*atan(1.0)
@@ -35,6 +36,9 @@ subroutine subtractft8(dd0,itone,f0,dt,lrefinedt)
      call four2a(cw,nfft,1,-1,1)
      cw=cw*fac
      first=.false.
+     do j=1,NFILT/2+1
+       endcorrection(j)=1.0/(1.0-sum(window(j-1:NFILT/2))/sumw)
+     enddo
   endif
 
 ! Generate complex reference waveform cref
@@ -72,7 +76,8 @@ contains
     call four2a(cfilt,nfft,1,-1,1)
     cfilt(1:nfft)=cfilt(1:nfft)*cw(1:nfft)
     call four2a(cfilt,nfft,1,1,1)
-
+    cfilt(1:NFILT/2+1)=cfilt(1:NFILT/2+1)*endcorrection
+    cfilt(nframe:nframe-NFILT/2:-1)=cfilt(nframe:nframe-NFILT/2:-1)*endcorrection
     x=0.
     do i=1,nframe
        j=nstart+i-1
diff --git a/lib/ft8/sync8.f90 b/lib/ft8/sync8.f90
index 0aa787629..997b1990d 100644
--- a/lib/ft8/sync8.f90
+++ b/lib/ft8/sync8.f90
@@ -37,7 +37,6 @@ subroutine sync8(dd,nfa,nfb,syncmin,nfqso,maxcand,s,candidate,   &
      enddo
      savg=savg + s(1:NH1,j)                   !Average spectrum
   enddo
-!  call baseline(savg,nfa,nfb,sbase)
   call get_spectrum_baseline(dd,nfa,nfb,sbase)
 
   ia=max(1,nint(nfa/df))
@@ -129,14 +128,13 @@ subroutine sync8(dd,nfa,nfb,syncmin,nfqso,maxcand,s,candidate,   &
   s=fac*s
 
 ! Sort by sync
-!  call indexx(candidate0(3,1:ncand),ncand,indx)
+  call indexx(candidate0(3,1:ncand),ncand,indx)
 ! Sort by frequency 
-  call indexx(candidate0(1,1:ncand),ncand,indx)
+!  call indexx(candidate0(1,1:ncand),ncand,indx)
   k=1
-!  do i=ncand,1,-1
-  do i=1,ncand
+  do i=ncand,1,-1
+!  do i=1,ncand
      j=indx(i)
-!     if( candidate0(3,j) .ge. syncmin .and. candidate0(2,j).ge.-1.5 ) then
      if( candidate0(3,j) .ge. syncmin ) then
        candidate(2:3,k)=candidate0(2:3,j)
        candidate(1,k)=abs(candidate0(1,j))
diff --git a/lib/ft8_decode.f90 b/lib/ft8_decode.f90
index 5fecc9bb6..dfdcc2060 100644
--- a/lib/ft8_decode.f90
+++ b/lib/ft8_decode.f90
@@ -115,8 +115,8 @@ contains
     if(ndepth.eq.1) npass=1
     if(ndepth.ge.2) npass=3
     do ipass=1,npass
-      newdat=.true.  ! Is this a problem? I hijacked newdat.
-      syncmin=1.5
+      newdat=.true.
+      syncmin=1.3
       if(ipass.eq.1) then
         lsubtract=.true.
         if(ndepth.eq.1) lsubtract=.false.
@@ -126,7 +126,7 @@ contains
         lsubtract=.true.
       elseif(ipass.eq.3) then
         if((ndecodes-n2).eq.0) cycle
-        lsubtract=.false. 
+        lsubtract=.true. 
       endif 
       call timer('sync8   ',0)
       maxc=MAXCAND