mirror of https://github.com/saitohirga/WSJT-X.git
348 lines
10 KiB
Fortran
348 lines
10 KiB
Fortran
subroutine ft4_decode(cdatetime0,tbuf,nfa,nfb,nfqso,iwave,ndecodes,mycall, &
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hiscall,nrx,line)
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use packjt77
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include 'ft4_params.f90'
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parameter (NSS=NSPS/NDOWN)
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character message*37
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character c77*77
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character*61 line,linex(100)
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character*37 decodes(100)
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character*120 data_dir
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character*17 cdatetime0
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character*6 mycall,hiscall,hhmmss
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complex cd2(0:NMAX/NDOWN-1) !Complex waveform
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complex cb(0:NMAX/NDOWN-1)
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complex cd(0:NN*NSS-1) !Complex waveform
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complex ctwk(4*NSS),ctwk2(4*NSS)
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complex csymb(NSS)
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complex cs(0:3,NN)
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real s4(0:3,NN)
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real bmeta(2*NN),bmetb(2*NN),bmetc(2*NN)
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real a(5)
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real llr(2*ND),llr2(2*ND),llra(2*ND),llrb(2*ND),llrc(2*ND)
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real s2(0:255)
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real candidate(3,100)
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real savg(NH1),sbase(NH1)
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integer nrxx(100)
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integer icos4(0:3)
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integer*2 iwave(NMAX) !Generated full-length waveform
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integer*1 message77(77),apmask(2*ND),cw(2*ND)
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integer*1 hbits(2*NN)
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integer graymap(0:3)
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integer ip(1)
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logical unpk77_success
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logical one(0:255,0:7) ! 256 4-symbol sequences, 8 bits
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logical first
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data icos4/0,1,3,2/
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data graymap/0,1,3,2/
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data first/.true./
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save one,first,nrxx,linex
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hhmmss=cdatetime0(8:13)
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fs=12000.0/NDOWN !Sample rate after downsampling
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dt=1/fs !Sample interval after downsample (s)
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tt=NSPS*dt !Duration of "itone" symbols (s)
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txt=NZ*dt !Transmission length (s) without ramp up/down
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twopi=8.0*atan(1.0)
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h=1.0
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if(first) then
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one=.false.
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do i=0,255
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do j=0,7
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if(iand(i,2**j).ne.0) one(i,j)=.true.
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enddo
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enddo
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first=.false.
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endif
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candidate=0.0
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ncand=0
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syncmin=1.2
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maxcand=100
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! ### This is temporary. Correct directory should be passed in as an argument.
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data_dir="."
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fa=nfa
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fb=nfb
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call getcandidates4(iwave,fa,fb,syncmin,nfqso,maxcand,savg,candidate, &
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ncand,sbase)
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ndecodes=0
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do icand=1,ncand
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f0=candidate(1,icand)
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xsnr=10*log10(candidate(3,icand))-18.0
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if( f0.le.375.0 .or. f0.ge.(5000.0-375.0) ) cycle
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call ft4_downsample(iwave,f0,cd2) ! downsample from 512 Sa/Symbol to 32 Sa/Symbol
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sum2=sum(cd2*conjg(cd2))/(real(NMAX)/real(NDOWN))
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if(sum2.gt.0.0) cd2=cd2/sqrt(sum2)
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! Sample rate is now 12000/16 = 750 samples/second
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do isync=1,2
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if(isync.eq.1) then
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idfmin=-50
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idfmax=50
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idfstp=3
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ibmin=0
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ibmax=374
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ibstp=4
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else
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idfmin=idfbest-5
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idfmax=idfbest+5
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idfstp=1
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ibmin=max(0,ibest-5)
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ibmax=min(ibest+5,NMAX/NDOWN-1)
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ibstp=1
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endif
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ibest=-1
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smax=-99.
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idfbest=0
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do idf=idfmin,idfmax,idfstp
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a=0.
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a(1)=real(idf)
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ctwk=1.
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call twkfreq1(ctwk,4*NSS,fs,a,ctwk2)
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do istart=ibmin,ibmax,ibstp
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call sync4d(cd2,istart,ctwk2,1,sync) !Find sync power
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if(sync.gt.smax) then
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smax=sync
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ibest=istart
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idfbest=idf
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endif
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enddo
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enddo
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enddo
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f0=f0+real(idfbest)
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call ft4_downsample(iwave,f0,cb) !Final downsample with corrected f0
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sum2=sum(abs(cb)**2)/(real(NSS)*NN)
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if(sum2.gt.0.0) cb=cb/sqrt(sum2)
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cd=cb(ibest:ibest+NN*NSS-1)
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do k=1,NN
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i1=(k-1)*NSS
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csymb=cd(i1:i1+NSS-1)
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call four2a(csymb,NSS,1,-1,1)
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cs(0:3,k)=csymb(1:4)
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s4(0:3,k)=abs(csymb(1:4))
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enddo
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! Sync quality check
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is1=0
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is2=0
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is3=0
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is4=0
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do k=1,4
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ip=maxloc(s4(:,k))
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if(icos4(k-1).eq.(ip(1)-1)) is1=is1+1
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ip=maxloc(s4(:,k+33))
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if(icos4(k-1).eq.(ip(1)-1)) is2=is2+1
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ip=maxloc(s4(:,k+66))
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if(icos4(k-1).eq.(ip(1)-1)) is3=is3+1
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ip=maxloc(s4(:,k+99))
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if(icos4(k-1).eq.(ip(1)-1)) is4=is4+1
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enddo
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nsync=is1+is2+is3+is4 !Number of hard sync errors, 0-16
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if(smax .lt. 0.9 .or. nsync .lt. 9) cycle
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do nseq=1,3 !Try coherent sequences of 1, 2, and 4 symbols
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if(nseq.eq.1) nsym=1
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if(nseq.eq.2) nsym=2
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if(nseq.eq.3) nsym=4
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nt=2**(2*nsym)
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do ks=1,NN-nsym+1,nsym !87+16=103 symbols.
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amax=-1.0
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do i=0,nt-1
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i1=i/64
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i2=iand(i,63)/16
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i3=iand(i,15)/4
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i4=iand(i,3)
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if(nsym.eq.1) then
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s2(i)=abs(cs(graymap(i4),ks))
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elseif(nsym.eq.2) then
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s2(i)=abs(cs(graymap(i3),ks)+cs(graymap(i4),ks+1))
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elseif(nsym.eq.4) then
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s2(i)=abs(cs(graymap(i1),ks ) + &
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cs(graymap(i2),ks+1) + &
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cs(graymap(i3),ks+2) + &
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cs(graymap(i4),ks+3) &
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)
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else
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print*,"Error - nsym must be 1, 2, or 4."
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endif
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enddo
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ipt=1+(ks-1)*2
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if(nsym.eq.1) ibmax=1
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if(nsym.eq.2) ibmax=3
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if(nsym.eq.4) ibmax=7
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do ib=0,ibmax
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bm=maxval(s2(0:nt-1),one(0:nt-1,ibmax-ib)) - &
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maxval(s2(0:nt-1),.not.one(0:nt-1,ibmax-ib))
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if(ipt+ib.gt.2*NN) cycle
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if(nsym.eq.1) then
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bmeta(ipt+ib)=bm
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elseif(nsym.eq.2) then
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bmetb(ipt+ib)=bm
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elseif(nsym.eq.4) then
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bmetc(ipt+ib)=bm
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endif
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enddo
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enddo
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enddo
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call normalizebmet(bmeta,2*NN)
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call normalizebmet(bmetb,2*NN)
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call normalizebmet(bmetc,2*NN)
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hbits=0
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where(bmeta.ge.0) hbits=1
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ns1=count(hbits( 1: 8).eq.(/0,0,0,1,1,0,1,1/))
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ns2=count(hbits( 67: 74).eq.(/0,0,0,1,1,0,1,1/))
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ns3=count(hbits(133:140).eq.(/0,0,0,1,1,0,1,1/))
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ns4=count(hbits(199:206).eq.(/0,0,0,1,1,0,1,1/))
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nsync_qual=ns1+ns2+ns3+ns4
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if(nsync_qual.lt. 20) cycle
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scalefac=2.83
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llra( 1: 58)=bmeta( 9: 66)
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llra( 59:116)=bmeta( 75:132)
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llra(117:174)=bmeta(141:198)
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llra=scalefac*llra
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llrb( 1: 58)=bmetb( 9: 66)
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llrb( 59:116)=bmetb( 75:132)
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llrb(117:174)=bmetb(141:198)
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llrb=scalefac*llrb
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llrc( 1: 58)=bmetc( 9: 66)
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llrc( 59:116)=bmetc( 75:132)
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llrc(117:174)=bmetc(141:198)
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llrc=scalefac*llrc
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do isd=1,3
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if(isd.eq.1) llr=llra
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if(isd.eq.2) llr=llrb
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if(isd.eq.3) llr=llrc
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apmask=0
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max_iterations=40
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do ibias=0,0
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llr2=llr
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if(ibias.eq.1) llr2=llr+0.4
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if(ibias.eq.2) llr2=llr-0.4
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call bpdecode174_91(llr2,apmask,max_iterations,message77, &
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cw,nharderror,niterations)
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if(nharderror.ge.0) exit
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enddo
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if(sum(message77).eq.0) cycle
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if( nharderror.ge.0 ) then
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write(c77,'(77i1)') message77(1:77)
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call unpack77(c77,1,message,unpk77_success)
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idupe=0
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do i=1,ndecodes
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if(decodes(i).eq.message) idupe=1
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enddo
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if(idupe.eq.1) exit
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ndecodes=ndecodes+1
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decodes(ndecodes)=message
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nsnr=nint(xsnr)
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freq=f0
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tsig=mod(tbuf + ibest/750.0,100.0)
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write(line,1000) hhmmss,nsnr,tsig,nint(freq),message
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1000 format(a6,i4,f5.1,i5,' + ',1x,a37)
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open(24,file='all_ft4.txt',status='unknown',position='append')
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write(24,1002) cdatetime0,nsnr,tsig,nint(freq),message, &
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nharderror,nsync_qual,isd,niterations
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if(hhmmss.eq.' ') write(*,1002) cdatetime0,nsnr, &
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tsig,nint(freq),message,nharderror,nsync_qual,isd, &
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niterations
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1002 format(a17,i4,f5.1,i5,' Rx ',a37,4i5)
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close(24)
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linex(ndecodes)=line
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!### Temporary: assume most recent decoded message conveys "hiscall". ###
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i0=index(message,' ')
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if(i0.ge.3 .and. i0.le.7) then
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hiscall=message(i0+1:i0+6)
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i1=index(hiscall,' ')
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if(i1.gt.0) hiscall=hiscall(1:i1)
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endif
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nrx=-1
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if(index(message,'CQ ').eq.1) nrx=1
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if((index(message,trim(mycall)//' ').eq.1) .and. &
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(index(message,' '//trim(hiscall)//' ').ge.4)) then
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if(index(message,' 559 ').gt.8) nrx=2 !### Not right !
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if(index(message,' R 559 ').gt.8) nrx=3 !### Not right !
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if(index(message,' RR73 ').gt.8) nrx=4
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endif
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nrxx(ndecodes)=nrx
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!###
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exit
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endif
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enddo !Sequence estimation
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enddo !Candidate list
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return
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entry get_ft4msg(idecode,nrx,line)
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line=linex(idecode)
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nrx=nrxx(idecode)
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return
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end subroutine ft4_decode
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subroutine ft4_downsample(iwave,f0,c)
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! Input: i*2 data in iwave() at sample rate 12000 Hz
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! Output: Complex data in c(), sampled at 1200 Hz
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include 'ft4_params.f90'
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parameter (NFFT2=NMAX/16)
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integer*2 iwave(NMAX)
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complex c(0:NMAX/NDOWN-1)
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complex c1(0:NFFT2-1)
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complex cx(0:NMAX/2)
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real x(NMAX), window(0:NFFT2-1)
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equivalence (x,cx)
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logical first
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data first/.true./
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save first,window
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df=12000.0/NMAX
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baud=12000.0/NSPS
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if(first) then
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bw_transition = 0.5*baud
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bw_flat = 4*baud
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iwt = bw_transition / df
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iwf = bw_flat / df
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pi=4.0*atan(1.0)
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window(0:iwt-1) = 0.5*(1+cos(pi*(/(i,i=iwt-1,0,-1)/)/iwt))
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window(iwt:iwt+iwf-1)=1.0
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window(iwt+iwf:2*iwt+iwf-1) = 0.5*(1+cos(pi*(/(i,i=0,iwt)/)/iwt))
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window(2*iwt+iwf:)=0.0
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iws = baud / df
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window=cshift(window,iws)
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first=.false.
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endif
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x=iwave
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call four2a(x,NMAX,1,-1,0) !r2c FFT to freq domain
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i0=nint(f0/df)
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c1=0.
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c1(0)=cx(i0)
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do i=1,NFFT2/2
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if(i0+i.le.NMAX/2) c1(i)=cx(i0+i)
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if(i0-i.ge.0) c1(NFFT2-i)=cx(i0-i)
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enddo
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c1=c1*window/NFFT2
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call four2a(c1,NFFT2,1,1,1) !c2c FFT back to time domain
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c=c1(0:NMAX/NDOWN-1)
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return
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end subroutine ft4_downsample
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