subroutine sync65(ss,nfa,nfb,naggressive,ntol,nhsym,ca,ncand,nrobust,   &
     single_decode)

  parameter (NSZ=3413,NFFT=8192,MAXCAND=300)
  real ss(322,NSZ)
  real ccfblue(-11:540)             !CCF with pseudorandom sequence
  real ccfred(NSZ)                  !Peak of ccfblue, as function of freq
  logical single_decode

  type candidate
     real freq
     real dt
     real sync
     real flip
  end type candidate
  type(candidate) ca(MAXCAND)

  common/steve/thresh0

  if(ntol.eq.-99) stop                       !Silence compiler warning
  call setup65
  df=12000.0/NFFT                            !df = 12000.0/8192 = 1.465 Hz
  ia=max(2,nint(nfa/df))
  ib=min(NSZ-1,nint(nfb/df))
  lag1=-11
  lag2=59
  nsym=126
  ncand=0
  fdot=0.
  ccfred=0.
  ccfblue=0.
  ccfmax=0.
  ipk=0

  do i=ia,ib
     call xcor(ss,i,nhsym,nsym,lag1,lag2,ccfblue,ccf0,lagpk0,flip,fdot,nrobust)
! Remove best-fit slope from ccfblue and normalize so baseline rms=1.0
     if(.not.single_decode) call slope(ccfblue(lag1),lag2-lag1+1,      &
          lagpk0-lag1+1.0)
     ccfred(i)=ccfblue(lagpk0)
     if(ccfred(i).gt.ccfmax) then
        ccfmax=ccfred(i)
        ipk=i
     endif
  enddo
  call pctile(ccfred(ia:ib),ib-ia+1,35,xmed)
  ccfred(ia:ib)=ccfred(ia:ib)-xmed
  ccfred(ia-1)=ccfred(ia)
  ccfred(ib+1)=ccfred(ib)

  do i=ia,ib
     freq=i*df
     itry=0
!     if(naggressive.gt.0 .and. ntol.lt.1000 .and. ccfmax.ge.thresh0) then
     if(naggressive.gt.0 .and. ccfmax.ge.thresh0) then
        if(i.ne.ipk) cycle
        itry=1
        ncand=ncand+1
     else
        if(ccfred(i).ge.thresh0 .and. ccfred(i).gt.ccfred(i-1) .and.       &
             ccfred(i).gt.ccfred(i+1)) then
           itry=1
           ncand=ncand+1
        endif
     endif
     if(itry.ne.0) then
        call xcor(ss,i,nhsym,nsym,lag1,lag2,ccfblue,ccf0,lagpk,flip,fdot,  &
             nrobust)
        if(.not.single_decode) call slope(ccfblue(lag1),lag2-lag1+1,       &
             lagpk-lag1+1.0)
        xlag=lagpk
        if(lagpk.gt.lag1 .and. lagpk.lt.lag2) then
           call peakup(ccfblue(lagpk-1),ccfmax,ccfblue(lagpk+1),dx2)
           xlag=lagpk+dx2
        endif
        dtx=xlag*2048.0/11025.0
        ccfblue(lag1)=0.
        ccfblue(lag2)=0.
        ca(ncand)%freq=freq
        ca(ncand)%dt=dtx
        ca(ncand)%flip=flip
        if(single_decode) then
           ca(ncand)%sync=db(ccfred(i)) - 16.0
        else
           ca(ncand)%sync=ccfred(i)
        endif
     endif
     if(ncand.eq.MAXCAND) exit
  enddo

  return
end subroutine sync65