WSJT-X/lib/redsync.f90

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subroutine redsync(ss,ntrperiod,ihsym,iz,red)
! Compute the red curve (approx JT9 sync amplitude).
! NB: red() is used for real-time display only. A better ccfred() is
! computed during the decode procedure.
Parameter (NSMAX=22000)
real*4 ss(184,NSMAX)
real*4 red(NSMAX)
include 'jt9sync.f90'
lagmax=9
if(ntrperiod.eq.2) lagmax=5
if(ntrperiod.eq.5) lagmax=2
if(ntrperiod.eq.10) lagmax=1
if(ntrperiod.eq.30) lagmax=1
do i=1,iz !Loop over frequency range
smax=0.
do lag=-lagmax,lagmax !Loop over DT lags
sig=0.
do j=1,16
k=ii2(j)+lag
if(k.ge.5 .and. k.le.ihsym) then
sig=sig + ss(k,i) - 0.5*(ss(k-2,i)+ss(k-4,i))
endif
enddo
if(sig.gt.smax) smax=sig
enddo
red(i)=smax
enddo
call pctile(red,iz,40,xmed)
if(xmed.le.0.0) xmed=1.0
red=red/xmed
smax=0.
do i=1,iz
red(i)=0.2*db(red(i))
smax=max(smax,red(i))
enddo
h=10.
if(smax.gt.h) red=red*(h/smax)
return
end subroutine redsync