mirror of https://github.com/saitohirga/WSJT-X.git
226 lines
6.3 KiB
Fortran
226 lines
6.3 KiB
Fortran
subroutine opdetmsk144(cbig,n,lines,nmessages,nutc,ntol,t00)
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use timer_module, only: timer
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! NSPM: number of samples per message frame
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! NAVG: number of frames to coherently average
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parameter (NSPM=864, NAVG=7, NPTS=NAVG*NSPM, NSTEP=6000)
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character*22 msgreceived,allmessages(20)
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character*80 lines(100)
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complex cbig(n)
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complex cdat(NPTS) !Analytic signal
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complex cdat2(NPTS)
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complex c(NSPM)
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complex cr(NSPM,NAVG)
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complex ct(NSPM)
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complex cs(NSPM)
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complex cb(42) !Complex waveform for sync word
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complex cfac,cca,ccb
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complex cc(0:NSPM-1)
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complex csum
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integer s8(8),hardbits(144)
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integer, dimension(1) :: iloc
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integer*1 decoded(80)
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integer ipeaks(10)
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real cbi(42),cbq(42)
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real rcw(12)
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real ccm(0:NSPM-1)
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real ccms(0:NSPM-1)
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real pp(12) !Half-sine pulse shape
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real*8 dt, fs, pi, twopi
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real softbits(144)
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real*8 lratio(128)
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real llr(128)
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logical first
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data first/.true./
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data s8/0,1,1,1,0,0,1,0/
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save first,cb,fs,pi,twopi,dt,s8,rcw,pp,nmatchedfilter
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if(first) then
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nmatchedfilter=1
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! define half-sine pulse and raised-cosine edge window
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pi=4d0*datan(1d0)
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twopi=8d0*datan(1d0)
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fs=12000.0
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dt=1.0/fs
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do i=1,12
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angle=(i-1)*pi/12.0
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pp(i)=sin(angle)
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rcw(i)=(1-cos(angle))/2
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enddo
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! define the sync word waveforms
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s8=2*s8-1
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cbq(1:6)=pp(7:12)*s8(1)
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cbq(7:18)=pp*s8(3)
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cbq(19:30)=pp*s8(5)
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cbq(31:42)=pp*s8(7)
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cbi(1:12)=pp*s8(2)
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cbi(13:24)=pp*s8(4)
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cbi(25:36)=pp*s8(6)
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cbi(37:42)=pp(1:6)*s8(8)
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cb=cmplx(cbi,cbq)
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first=.false.
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endif
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nmessages=0
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allmessages=char(0)
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lines=char(0)
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nshort=0
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trec=NPTS/12000.0 ! Duration of the data record
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! write(*,*) "number of points in opdetmsk144",n
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if( n .lt. NPTS .or. n .gt. 181000) return
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nsteps=2*n/NSTEP-1 ! Hardwired for 0.5s steps
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! write(*,*) 'nsteps ',nsteps
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nsnr=-4
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do istep=1,nsteps
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ib=(istep-1)*NPTS/2+1
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ie=ib+NPTS-1
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if( ie .gt. n ) then
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ie=n
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ib=n-NPTS+1
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endif
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t0=t00+(ib-1)/12000.0+trec/2
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cdat=cbig(ib:ie)
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xmax=0.0
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bestf=0.0
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do ifr=-ntol,ntol ! search for frequency that maximizes sync correlation
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ferr=ifr
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! call timer('opdetavg ',0)
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call tweak1(cdat,NPTS,-(1500+ferr),cdat2)
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cr=reshape(cdat2,(/NSPM,NAVG/))
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c=sum(cr,2)
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! call timer('opdetavg ',1)
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! call timer('opdetsync',0)
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cc=0
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do ish=0,NSPM-1
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ct=cshift(c,ish)
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! cc(ish)=sum(ct(1:42)*conjg(cb))+sum(ct(56*6:56*6+41)*conjg(cb))
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! cc(ish)=sum(ct(1:42)*conjg(cb)+ ct(56*6:56*6+41)*conjg(cb))
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csum=0
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do j=1,42
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csum=csum+(ct(j)+ct(56*6+j-1))*conjg(cb(j))
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enddo
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cc(ish)=csum
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enddo
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ccm=abs(cc)
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xb=maxval(ccm)
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! call timer('opdetsync',1)
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if( xb .gt. xmax ) then
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xmax=xb
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bestf=ferr
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cs=c
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ccms=ccm
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endif
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enddo
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fest=1500+bestf
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! write(*,*) istep,fest,xmax
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c=cs
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ccm=ccms
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! Find 2 largest peaks
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do ipk=1, 2
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iloc=maxloc(ccm)
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ic2=iloc(1)
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ipeaks(ipk)=ic2
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ccm(max(0,ic2-7):min(NSPM-1,ic2+7))=0.0
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enddo
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do ipk=1,2
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do is=1,3
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ic0=ipeaks(ipk)
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if( is.eq.2 ) ic0=max(1,ic0-1)
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if( is.eq.3 ) ic0=min(NSPM,ic0+1)
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ct=cshift(c,ic0-1)
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! Estimate final frequency error and carrier phase.
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cca=sum(ct(1:1+41)*conjg(cb))
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ccb=sum(ct(1+56*6:1+56*6+41)*conjg(cb))
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cfac=ccb*conjg(cca)
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ffin=atan2(imag(cfac),real(cfac))/(twopi*56*6*dt)
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phase0=atan2(imag(cca+ccb),real(cca+ccb))
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! Remove phase error - want constellation rotated so that sample points lie on I/Q axes
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cfac=cmplx(cos(phase0),sin(phase0))
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ct=ct*conjg(cfac)
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if( nmatchedfilter .eq. 0 ) then
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! sample to get softsamples
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do i=1,72
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softbits(2*i-1)=imag(c(1+(i-1)*12))
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softbits(2*i)=real(c(7+(i-1)*12))
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enddo
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else
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! matched filter -
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softbits(1)=sum(imag(ct(1:6))*pp(7:12))+sum(imag(ct(864-5:864))*pp(1:6))
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softbits(2)=sum(real(ct(1:12))*pp)
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do i=2,72
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softbits(2*i-1)=sum(imag(ct(1+(i-1)*12-6:1+(i-1)*12+5))*pp)
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softbits(2*i)=sum(real(ct(7+(i-1)*12-6:7+(i-1)*12+5))*pp)
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enddo
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endif
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! sync word hard error weight is a good discriminator for
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! frames that have reasonable probability of decoding
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hardbits=0
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do i=1,144
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if( softbits(i) .ge. 0.0 ) then
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hardbits(i)=1
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endif
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enddo
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nbadsync1=(8-sum( (2*hardbits(1:8)-1)*s8 ) )/2
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nbadsync2=(8-sum( (2*hardbits(1+56:8+56)-1)*s8 ) )/2
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nbadsync=nbadsync1+nbadsync2
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!write(*,*) 'peak index ',ipk,' pk loc: ',ic0,' nbadsync ',nbadsync
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if( nbadsync .gt. 4 ) cycle
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! normalize the softsymbols before submitting to decoder
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sav=sum(softbits)/144
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s2av=sum(softbits*softbits)/144
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ssig=sqrt(s2av-sav*sav)
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softbits=softbits/ssig
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sigma=0.75
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lratio(1:48)=softbits(9:9+47)
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lratio(49:128)=softbits(65:65+80-1)
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llr=2.0*lratio/(sigma*sigma)
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lratio=exp(2.0*lratio/(sigma*sigma))
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max_iterations=10
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max_dither=1
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call timer('bpdec144 ',0)
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call bpdecode144(llr,max_iterations,decoded,niterations)
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call timer('bpdec144 ',1)
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if( niterations .ge. 0.0 ) then
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call extractmessage144(decoded,msgreceived,nhashflag)
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if( nhashflag .gt. 0 ) then ! CRCs match, so print it
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ndupe=0
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do im=1,nmessages
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if( allmessages(im) .eq. msgreceived ) ndupe=1
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enddo
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if( ndupe .eq. 0 ) then
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nmessages=nmessages+1
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allmessages(nmessages)=msgreceived
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write(lines(nmessages),1020) nutc,nsnr,t0,nint(fest),msgreceived
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1020 format(i6.6,i4,f5.1,i5,' ^ ',a22)
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endif
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goto 999
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else
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msgreceived=' '
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ndither=-99 ! -99 is bad hash flag
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endif
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endif
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enddo ! slicer dither
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enddo ! peak loop
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enddo
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msgreceived=' '
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ndither=-98
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999 continue
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return
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end subroutine opdetmsk144
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