FT4: Improve sync performance on disturbed channels. Make jt9 command-line option -d work

lib/ft4/sync4d.f90

@@ -9,7 +9,6 @@ subroutine sync4d(cd0,i0,ctwk,itwk,sync)
   complex csync2(2*NSS)
   complex ctwk(2*NSS)
   complex z1,z2,z3,z4
-  complex zz1,zz2,zz3,zz4
   logical first
   integer icos4a(0:3),icos4b(0:3),icos4c(0:3),icos4d(0:3)
   data icos4a/0,1,3,2/
@@ -19,7 +18,7 @@ subroutine sync4d(cd0,i0,ctwk,itwk,sync)
   data first/.true./
   save first,twopi,csynca,csyncb,csyncc,csyncd,fac
 
-  p(z1)=real(z1*fac)**2 + aimag(z1*fac)**2          !Statement function for power
+  p(z1)=sqrt(real(z1*fac)**2 + aimag(z1*fac)**2)          !Statement function for power
 
   if( first ) then
     twopi=8.0*atan(1.0)
@@ -60,11 +59,12 @@ subroutine sync4d(cd0,i0,ctwk,itwk,sync)
   z4=0.
 
   if(itwk.eq.1) csync2=ctwk*csynca      !Tweak the frequency
+  z1=0.
   if(i1.ge.0 .and. i1+4*NSS-1.le.NP-1) then
     z1=sum(cd0(i1:i1+4*NSS-1:2)*conjg(csync2))
   elseif( i1.lt.0 ) then
     npts=(i1+4*NSS-1)/2
-    if(npts.le.8) then
+    if(npts.le.16) then
       z1=0.
     else
       z1=sum(cd0(0:i1+4*NSS-1:2)*conjg(csync2(2*NSS-npts:)))
@@ -78,16 +78,18 @@ subroutine sync4d(cd0,i0,ctwk,itwk,sync)
   if(i3.ge.0 .and. i3+4*NSS-1.le.NP-1) z3=sum(cd0(i3:i3+4*NSS-1:2)*conjg(csync2))
 
   if(itwk.eq.1) csync2=ctwk*csyncd      !Tweak the frequency
+  z4=0.
   if(i4.ge.0 .and. i4+4*NSS-1.le.NP-1) then
     z4=sum(cd0(i4:i4+4*NSS-1:2)*conjg(csync2))
   elseif( i4+4*NSS-1.gt.NP-1 ) then
     npts=(NP-1-i4+1)/2
-    if(npts.le.8) then
+    if(npts.le.16) then
       z4=0.
     else
       z4=sum(cd0(i4:i4+2*npts-1:2)*conjg(csync2(1:npts)))
     endif
   endif
+
   sync = p(z1) + p(z2) + p(z3) + p(z4)
 
   return

lib/ft4_decode.f90

@@ -285,12 +285,10 @@ contains
             else
                cd(-ibest:ibest+NN*NSS-1)=cb(0:NN*NSS+2*ibest-1)
             endif 
-
             call timer('bitmet  ',0)
             call get_ft4_bitmetrics(cd,bitmetrics,badsync)
             call timer('bitmet  ',1)
             if(badsync) cycle
-
             hbits=0
             where(bitmetrics(:,1).ge.0) hbits=1
             ns1=count(hbits(  1:  8).eq.(/0,0,0,1,1,0,1,1/))
@@ -405,7 +403,7 @@ contains
 
                if(doosd .and. nharderror.lt.0) then
                   ndeep=3
-                  if(abs(nfqso-f1).le.napwid) then
+                  if(abs(nfqso-f0).le.napwid) then
                      ndeep=4
                   endif
                   call timer('osd174_91 ',0)
@@ -439,7 +437,8 @@ contains
                   endif
                   nsnr=nint(max(-21.0,xsnr))
                   xdt=ibest/666.67 - 0.5
-!write(21,'(i6.6,i5,2x,f4.1,i6,2x,a37,2x,f4.1,3i3,f5.1)') nutc,nsnr,xdt,nint(f0),message,sync,iaptype,ipass,isp,dmin
+!write(21,'(i6.6,i5,2x,f4.1,i6,2x,a37,2x,f4.1,3i3,f5.1,i4,i4)') & 
+!  nutc,nsnr,xdt,nint(f0),message,sync,iaptype,ipass,isp,dmin,nsync_qual,nharderror
                   call this%callback(sync,nsnr,xdt,f0,message,iaptype,qual)
                   exit
                endif

lib/jt9.f90

@@ -179,7 +179,6 @@ program jt9
      go to 999
   endif
 
-  if(mode.eq.5) ndepth=3
   allocate(shared_data)
   nflatten=0