Initial Commit

2018-02-08 21:28:33 -05:00
commit 678c1d3966
14352 changed files with 3176737 additions and 0 deletions
@@ -0,0 +1,112 @@
+program ft8d
+
+! Decode FT8 data read from *.wav files.
+
+! FT8 is a potential mode intended for use at 6m (and maybe HF).  It uses an
+! LDPC (174,87) code, 8-FSK modulation, and 15 second T/R sequences.  Otherwise
+! should behave like JT65 and JT9 as used on HF bands, except that QSOs are
+! 4 x faster.
+
+! Reception and Demodulation algorithm:
+!   ... tbd ...
+
+  include 'ft8_params.f90'
+  parameter(NRECENT=10)
+  character*12 recent_calls(NRECENT)
+  character message*22,infile*80,datetime*13
+  real s(NH1,NHSYM)
+  real s1(0:7,ND)
+  real ps(0:7)
+  real rxdata(3*ND),llr(3*ND)               !Soft symbols
+  integer ihdr(11)
+  integer*2 iwave(NMAX)                 !Generated full-length waveform  
+!  integer*1 idat(7)
+  integer*1 decoded(KK),apmask(ND),cw(ND)
+
+  nargs=iargc()
+  if(nargs.lt.1) then
+     print*,'Usage:   ft8d file1 [file2 ...]'
+     go to 999
+  endif
+
+  twopi=8.0*atan(1.0)
+  fs=12000.0                             !Sample rate
+  dt=1.0/fs                              !Sample interval (s)
+  tt=NSPS*dt                             !Duration of "itone" symbols (s)
+  ts=2*NSPS*dt                           !Duration of OQPSK symbols (s)
+  baud=1.0/tt                            !Keying rate (baud)
+  txt=NZ*dt                              !Transmission length (s)
+
+  do ifile=1,nargs
+     call getarg(ifile,infile)
+     open(10,file=infile,status='old',access='stream')
+     read(10,end=999) ihdr,iwave
+     close(10)
+     j2=index(infile,'.wav')
+     read(infile(j2-6:j2-1),*) nutc
+     datetime=infile(j2-13:j2-1)
+     call sync8(iwave,xdt,f1,s)
+
+     xsnr=0.
+     tstep=0.5*NSPS/12000.0
+     df=12000.0/NFFT1
+     i0=nint(f1/df)
+     j0=nint(xdt/tstep)
+     fac=20.0/maxval(s)
+     s=fac*s
+
+     j=0
+     ia=i0
+     ib=i0+14
+     do k=1,NN
+        if(k.le.7) cycle
+        if(k.ge.37 .and. k.le.43) cycle
+        if(k.gt.72) cycle
+        n=j0+2*(k-1)+1
+        if(n.lt.1) cycle
+        j=j+1
+        s1(0:7,j)=s(ia:ib:2,n)
+     enddo
+
+     do j=1,ND
+        ps=s1(0:7,j)
+        ps=log(ps)
+        r1=max(ps(1),ps(3),ps(5),ps(7))-max(ps(0),ps(2),ps(4),ps(6))
+        r2=max(ps(2),ps(3),ps(6),ps(7))-max(ps(0),ps(1),ps(4),ps(5))
+        r4=max(ps(4),ps(5),ps(6),ps(7))-max(ps(0),ps(1),ps(2),ps(3))
+        rxdata(3*j-2)=r4
+        rxdata(3*j-1)=r2
+        rxdata(3*j)=r1
+     enddo
+     rxav=sum(rxdata)/ND
+     rx2av=sum(rxdata*rxdata)/ND
+     rxsig=sqrt(rx2av-rxav*rxav)
+     rxdata=rxdata/rxsig
+     ss=0.84
+     llr=2.0*rxdata/(ss*ss)
+     apmask=0
+     max_iterations=40
+     ifer=0
+     call bpdecode174(llr,apmask,max_iterations,decoded,niterations)
+     if(niterations.lt.0) then
+        write(41,*) llr,apmask,max_iterations,decoded,niterations
+        call osd174(llr,2,decoded,niterations,cw)
+        write(42,*) llr,apmask,max_iterations,decoded,niterations
+!        if(niterations.lt.0) stop
+     endif
+     nbadcrc=0
+     if(niterations.ge.0) call chkcrc12a(decoded,nbadcrc)
+     if(niterations.lt.0 .or. nbadcrc.ne.0) ifer=1
+
+     message='                      '
+     if(ifer.eq.0) then
+        call extractmessage174(decoded,message,ncrcflag,recent_calls,nrecent)
+     endif
+     nsnr=nint(xsnr)
+     write(13,1110) datetime,0,nsnr,xdt,freq,message,nfdot
+1110 format(a11,2i4,f6.2,f12.7,2x,a22,i3)
+     write(*,1112) datetime(8:13),nsnr,xdt,nint(f1),message
+1112 format(a6,i4,f5.1,i6,2x,a22)
+  enddo                                   ! ifile loop
+
+999 end program ft8d