197 lines
5.1 KiB
Plaintext
197 lines
5.1 KiB
Plaintext
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program msk144sd
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!
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! A simple decoder for slow msk144.
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! Can be used as a (slow) brute-force multi-decoder by looping
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! over a set of carrier frequencies.
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!
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use options
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use timer_module, only: timer
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use timer_impl, only: init_timer
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use readwav
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parameter (NRECENT=10)
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parameter (NSPM=864)
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parameter (NPATTERNS=4)
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character ch
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character*80 line
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character*500 infile
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character*12 mycall,hiscall
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character*6 mygrid
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character(len=500) optarg
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character*22 msgreceived
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character*12 recent_calls(NRECENT)
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complex cdat(30*375)
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complex c(NSPM)
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complex ct(NSPM)
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real softbits(144)
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real xmc(NPATTERNS)
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logical :: display_help=.false.
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type(wav_header) :: wav
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integer iavmask(8)
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integer iavpatterns(8,NPATTERNS)
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integer npkloc(10)
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integer*2 id2(30*12000)
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integer*2 ichunk(7*1024)
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data iavpatterns/ &
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1,1,1,1,0,0,0,0, &
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0,0,1,1,1,1,0,0, &
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1,1,1,1,1,0,0,0, &
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1,1,1,1,1,1,0,0/
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data xmc/2.0,4.5,2.5,3.0/
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type (option) :: long_options(2) = [ &
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option ('frequency',.true.,'f','rxfreq',''), &
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option ('help',.false.,'h','Display this help message','') &
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]
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t0=0.0
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ntol=100
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nrxfreq=1500
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do
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call getopt('f:h',long_options,ch,optarg,narglen,nstat,noffset,nremain,.true.)
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if( nstat .ne. 0 ) then
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exit
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end if
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select case (ch)
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case ('f')
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read (optarg(:narglen), *) nrxfreq
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case ('h')
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display_help = .true.
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end select
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end do
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if(display_help .or. nstat.lt.0 .or. nremain.lt.1) then
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print *, ''
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print *, 'Usage: msk144sd [OPTIONS] file1 [file2 ...]'
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print *, ''
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print *, ' decode pre-recorded .WAV file(s)'
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print *, ''
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print *, 'OPTIONS:'
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do i = 1, size (long_options)
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call long_options(i) % print (6)
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end do
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go to 999
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endif
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call init_timer ('timer.out')
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call timer('msk144 ',0)
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ndecoded=0
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do ifile=noffset+1,noffset+nremain
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call get_command_argument(ifile,optarg,narglen)
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infile=optarg(:narglen)
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call timer('read ',0)
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call wav%read (infile)
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i1=index(infile,'.wav')
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if( i1 .eq. 0 ) i1=index(infile,'.WAV')
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read(infile(i1-6:i1-1),*,err=998) nutc
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inquire(FILE=infile,SIZE=isize)
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npts=min((isize-216)/2,360000)
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read(unit=wav%lun) id2(1:npts)
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close(unit=wav%lun)
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call timer('read ',1)
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! do if=1,89 ! brute force multi-decoder
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fo=nrxfreq
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! fo=(if-1)*25.0+300.0
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call msksddc(id2,npts,fo,cdat)
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np=npts/32
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ntol=200 ! actual ntol is ntol/32=6.25 Hz. Detection window is 12.5 Hz wide
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fc=1500.0
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call msk144spd(cdat,np,ntol,ndecodesuccess,msgreceived,fc,fest,tdec,navg,ct, &
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softbits,recent_calls,nrecent)
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nsnr=0 ! need an snr estimate
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if( ndecodesuccess .eq. 1 ) then
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fest=fo+fest-fc ! fudging because spd thinks input signal is at 1500 Hz
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goto 900
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endif
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! If short ping decoder doesn't find a decode
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npat=NPATTERNS
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do iavg=1,npat
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iavmask=iavpatterns(1:8,iavg)
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navg=sum(iavmask)
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deltaf=4.0/real(navg) ! search increment for frequency sync
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npeaks=3
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ntol=200
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fc=1500.0
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call msk144sync(cdat(1:6*NSPM),6,ntol,deltaf,iavmask,npeaks,fc, &
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fest,npkloc,nsyncsuccess,xmax,c)
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if( nsyncsuccess .eq. 0 ) cycle
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do ipk=1,npeaks
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do is=1,3
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ic0=npkloc(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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call msk144decodeframe(ct,softbits,msgreceived,ndecodesuccess, &
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recent_calls,nrecent)
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if(ndecodesuccess .gt. 0) then
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tdec=tsec+xmc(iavg)*tframe
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fest=fo+(fest-fc)/32.0
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goto 900
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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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! enddo
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900 continue
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if( ndecodesuccess .gt. 0 ) then
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write(*,1020) nutc,nsnr,tdec,nint(fest),' % ',msgreceived,navg
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1020 format(i6.6,i4,f5.1,i5,a3,a22,i4)
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endif
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enddo
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call timer('msk144 ',1)
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call timer('msk144 ',101)
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go to 999
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998 print*,'Cannot read from file:'
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print*,infile
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999 continue
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end program msk144sd
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subroutine msksddc(id2,npts,fc,cdat)
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! The msk144 detector/demodulator/decoder will decode signals
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! with carrier frequency, fc, in the range fN/4 +/- 0.03333*fN.
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!
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! For slow MSK144 with nslow=32:
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! fs=12000/32=375 Hz, fN=187.5 Hz
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!
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! This routine accepts input samples with fs=12000 Hz. It
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! downconverts and decimates by 32 to center a signal with input carrier
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! frequency fc at new carrier frequency 1500/32=46.875 Hz.
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! The analytic signal is returned.
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parameter (NFFT1=30*12000,NFFT2=30*375)
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integer*2 id2(npts)
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complex cx(0:NFFT1)
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complex cdat(30*375)
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dt=1.0/12000.0
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df=1.0/(NFFT1*dt)
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icenter=int(fc/df+0.5)
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i46p875=int(46.875/df+0.5)
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ishift=icenter-i46p875
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cx=cmplx(0.0,0.0)
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cx(1:npts)=id2
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call four2a(cx,NFFT1,1,-1,1)
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cx=cshift(cx,ishift)
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cx(2*i46p875+1:)=cmplx(0.0,0.0)
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call four2a(cx,NFFT2,1,1,1)
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cdat(1:npts/32)=cx(0:npts/32-1)/NFFT1
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return
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end subroutine msksddc
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