WSJT-X/lib/ft8/ft8q3.f90

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Fortran
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subroutine ft8q3(cd,xdt,f0,call_1,call_2,grid4,msgbest,snr)
! Get q3-style decodes for FT8.
use packjt77
parameter(NN=79,NSPS=32)
parameter(NWAVE=NN*NSPS) !2528
parameter(NZ=3200,NLAGS=NZ-NWAVE)
character*12 call_1,call_2
character*4 grid4
character*37 msg,msgbest,msgsent
character c77*77
complex cwave(0:NWAVE-1)
complex cd(0:NZ-1)
complex z
real xjunk(NWAVE)
real ccf(0:NLAGS-1)
real ccfmsg(207)
integer itone(NN)
integer*1 msgbits(77)
logical std_1,std_2
if(xdt.eq.-99.0) return !Silence compiler warning
call stdcall(call_1,std_1)
call stdcall(call_2,std_2)
fs=200.0 !Sample rate (Hz)
dt=1.0/fs !Sample interval (s)
bt=2.0
ccfbest=0.
lagbest=-1
do imsg=1,207
msg=trim(call_1)//' '//trim(call_2)
i=imsg
if(.not.std_1) then
if(i.eq.1 .or. i.ge.6) msg='<'//trim(call_1)//'> '//trim(call_2)
if(i.ge.2 .and. i.le.4) msg=trim(call_1)//' <'//trim(call_2)//'>'
else if(.not.std_2) then
if(i.le.4 .or. i.eq.6) msg='<'//trim(call_1)//'> '//trim(call_2)
if(i.ge.7) msg=trim(call_1)//' <'//trim(call_2)//'>'
endif
j0=len(trim(msg))+2
if(i.eq.2) msg(j0:j0+2)='RRR'
if(i.eq.3) msg(j0:j0+3)='RR73'
if(i.eq.4) msg(j0:j0+1)='73'
if(i.eq.5) then
if(std_2) msg='CQ '//trim(call_2)//' '//grid4
if(.not.std_2) msg='CQ '//trim(call_2)
endif
if(i.eq.6 .and. std_2) msg(j0:j0+3)=grid4
if(i.ge.7 .and. i.le.206) then
isnr = -50 + (i-7)/2
if(iand(i,1).eq.1) then
write(msg(j0:j0+2),'(i3.2)') isnr
if(msg(j0:j0).eq.' ') msg(j0:j0)='+'
else
write(msg(j0:j0+3),'("R",i3.2)') isnr
if(msg(j0+1:j0+1).eq.' ') msg(j0+1:j0+1)='+'
endif
endif
if(i.eq.207) msg='TNX 73 GL'
! Source-encode, then get itone()
i3=-1
n3=-1
call pack77(msg,i3,n3,c77)
call genft8(msg,i3,n3,msgsent,msgbits,itone)
! Generate complex cwave
call gen_ft8wave(itone,NN,NSPS,bt,fs,f0,cwave,xjunk,1,NWAVE)
if(imsg.eq.79) then
print*,NN,NSPS,bt,fs,f0,NWAVE,itone(1:7)
do i=0,NWAVE-1
write(45,3045) i,cd(i),100*cwave(i)
3045 format(i5,4e12.3)
enddo
endif
lagmax=-1
ccfmax=0.
nsum=32*2
do lag=0,nlags-1
z=0.
s=0.
do i=0,NWAVE-1
z=z + cd(i+lag)*conjg(cwave(i))
if(mod(i,nsum).eq.nsum-1 .or. i.eq.NWAVE-1) then
s=s + abs(z)
z=0.
endif
enddo
ccf(lag)=s
if(ccf(lag).gt.ccfmax) then
ccfmax=ccf(lag)
lagmax=lag
endif
enddo ! lag
ccfmsg(imsg)=ccfmax
if(ccfmax.gt.ccfbest) then
ccfbest=ccfmax
lagbest=lagmax
msgbest=msg
endif
enddo ! imsg
call pctile(ccfmsg,207,50,base)
call pctile(ccfmsg,207,67,sigma)
sigma=sigma-base
ccfmsg=(ccfmsg-base)/(2.5*sigma)
! do imsg=1,207
! write(44,3044) imsg,ccfmsg(imsg)
!3044 format(i5,f10.3)
! enddo
snr=maxval(ccfmsg)
return
end subroutine ft8q3