WSJT-X/libm65/ccf2.f

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subroutine ccf2(ss,nz,nflip,ccfbest,lagpk)
parameter (LAGMAX=60)
! parameter (LAGMAX=200)
real ss(nz)
real ccf(-LAGMAX:LAGMAX)
integer npr(126)
C The JT65 pseudo-random sync pattern:
data npr/
+ 1,0,0,1,1,0,0,0,1,1,1,1,1,1,0,1,0,1,0,0,
+ 0,1,0,1,1,0,0,1,0,0,0,1,1,1,0,0,1,1,1,1,
+ 0,1,1,0,1,1,1,1,0,0,0,1,1,0,1,0,1,0,1,1,
+ 0,0,1,1,0,1,0,1,0,1,0,0,1,0,0,0,0,0,0,1,
+ 1,0,0,0,0,0,0,0,1,1,0,1,0,0,1,0,1,1,0,1,
+ 0,1,0,1,0,0,1,1,0,0,1,0,0,1,0,0,0,0,1,1,
+ 1,1,1,1,1,1/
save
ccfbest=0.
lag1=-LAGMAX
lag2=LAGMAX
do lag=lag1,lag2
s0=0.
s1=0.
do i=1,126
j=2*(8*i + 43) + lag
if(j.ge.1 .and. j.le.nz-8) then
x=ss(j)+ss(j+8) !Add two half-symbol contributions
if(npr(i).eq.0) then
s0=s0 + x
else
s1=s1 + x
endif
endif
enddo
ccf(lag)=nflip*(s1-s0)
if(ccf(lag).gt.ccfbest) then
ccfbest=ccf(lag)
lagpk=lag
endif
enddo
return
end