mirror of https://github.com/saitohirga/WSJT-X.git
162 lines
4.4 KiB
Fortran
162 lines
4.4 KiB
Fortran
subroutine jtmsk_short(cdat,npts,narg,tbest,idfpk,decoded)
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! Decode short-format messages in JTMSK mode.
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parameter (NMAX=15*12000,NSAVE=100)
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character*22 msg,decoded,msgsent
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character*3 rpt(0:7)
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complex cdat(0:npts-1)
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complex cw(0:209,0:4095) !Waveforms of possible messages
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complex cb11(0:65) !Complex waveform of Barker 11
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complex cd(0:511)
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complex z1,z2a,z2b
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real*8 dt,twopi,freq,phi,dphi0,dphi1,dphi
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real r1(0:NMAX-1)
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real r2(0:4095)
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real r1save(NSAVE)
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integer itone(234) !Message bits
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integer jgood(NSAVE)
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integer indx(NSAVE)
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integer narg(0:14)
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logical first
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data rpt /'26 ','27 ','28 ','R26','R27','R28','RRR','73 '/
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data first/.true./,nrxfreq0/-1/,ttot/0.0/
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save first,cw,cb11,nrxfreq0,ttot
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nrxfreq=narg(10) !Target Rx audio frequency (Hz)
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ntol=narg(11) !Search range, +/- ntol (Hz)
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nhashcalls=narg(12)
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if(first .or. nrxfreq.ne.nrxfreq0) then
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dt=1.d0/12000.d0
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twopi=8.d0*atan(1.d0)
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freq=nrxfreq
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dphi0=twopi*(freq-500.d0)*dt !Phase increment, lower tone
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dphi1=twopi*(freq+500.d0)*dt !Phase increment, upper tone
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nsym=35 !Number of symbols
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nspm=6*nsym !Samples per message
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msg="<C1ALL C2ALL> 73"
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do imsg=0,4095 !Generate all possible message waveforms
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ichk=10000+imsg
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call genmsk(msg,ichk,msgsent,itone,itype) !Encode the message
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k=-1
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phi=0.d0
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do j=1,nsym
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dphi=dphi0
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if(itone(j).eq.1) dphi=dphi1
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do i=1,6
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k=k+1
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phi=phi + dphi
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if(phi.gt.twopi) phi=phi-twopi
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xphi=phi
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cw(k,imsg)=cmplx(cos(xphi),sin(xphi))
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enddo
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enddo
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enddo
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cb11=cw(0:65,0)
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first=.false.
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nrxfreq0=nrxfreq
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endif
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r1thresh=0.80
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maxdecodes=999
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r1max=0.
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do j=0,npts-210 !Find the B11 sync vectors
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z1=0.
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ss=0.
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do i=0,65
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ss=ss + real(cdat(j+i))**2 + aimag(cdat(j+i))**2
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z1=z1 + cdat(j+i)*conjg(cb11(i)) !Signal matching B11
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enddo
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ss=sqrt(ss/66.0)*66.0
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r1(j)=abs(z1)/(0.908*ss) !Goodness-of-fit to B11
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if(r1(j).gt.r1max) then
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r1max=r1(j)
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jpk=j
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endif
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enddo
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k=0
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do j=1,npts-211
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if(r1(j).gt.r1thresh .and. r1(j).ge.r1(j-1) .and. r1(j).ge.r1(j+1) ) then
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k=k+1
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jgood(k)=j
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r1save(k)=r1(j)
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if(k.ge.NSAVE) exit
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endif
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enddo
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kmax=k
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call indexx(r1save,kmax,indx)
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df=12000.0/512.0
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ibest2=-1
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idfbest=0
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u1best=0.
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do kk=1,min(kmax,10)
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k=indx(kmax+1-kk)
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j=jgood(k)
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if(j.lt.144 .or. j.gt.npts-210) cycle
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t=j/12000.0
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u1=0.
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u2=0.
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r2max=0.
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ibest=-1
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do iidf=0,10
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idf=20*((iidf+1)/2)
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if(idf.gt.ntol) exit
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if(iand(iidf,1).eq.1) idf=-idf
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call tweak1(cdat(j-144:j+209),354,float(-idf),cd)
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cd(354:)=0.
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do imsg=0,4095
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ssa=0.
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ssb=0.
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do i=0,209
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ssa=ssa + real(cd(144+i))**2 + aimag(cd(144+i))**2
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ssb=ssb + real(cd(i))**2 + aimag(cdat(i))**2
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enddo
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z2a=dot_product(cw(0:209,imsg),cd(144:353))
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z2b=dot_product(cw(0:65,imsg),cdat(144:209)) + &
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dot_product(cw(66:209,imsg),cdat(0:143))
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ssa=sqrt(ssa/210.0)*210.0
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ssb=sqrt(ssb/210.0)*210.0
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r2(imsg)=max(abs(z2a)/ssa,abs(z2b)/ssb)
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if(r2(imsg).gt.r2max) then
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r2max=r2(imsg)
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ibest=imsg
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u2=u1
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u1=r2max
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idfpk=idf
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t2=t
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n=0
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if(imsg.eq.2296 .or. imsg.eq.2302) n=1
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endif
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enddo
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enddo
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r1_r2=r1(j)/r2max
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if(u1.ge.0.71 .and. u2/u1.lt.0.91 .and. r1_r2.lt.1.3) then
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if(u1.gt.u1best) then
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irpt=iand(ibest,7)
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ihash=ibest/8
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narg(13)=ibest
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decoded="<...> "//rpt(irpt)
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tbest=t
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r1best=r1(j)
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u1best=u1
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u2best=u2
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ibest2=ibest
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idfbest=idfpk
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r1_r2best=r1_r2
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nn=0
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if(ihash.eq.narg(12) .and. iand(ibest2,7).eq.0) nn=1
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endif
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endif
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enddo
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return
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end subroutine jtmsk_short
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