2018-02-08 21:28:33 -05:00
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subroutine decode65a(dd,npts,newdat,nqd,f0,nflip,mode65,ntrials, &
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2018-03-05 14:49:51 -05:00
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naggressive,ndepth,ntol,mycall,hiscall,hisgrid,nQSOProgress, &
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ljt65apon, nexp_decode, &
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2018-02-08 21:28:33 -05:00
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bVHF,sync2,a,dt,nft,nspecial,qual,nhist,nsmo,decoded)
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! Apply AFC corrections to a candidate JT65 signal, then decode it.
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use jt65_mod
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use timer_module, only: timer
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parameter (NMAX=60*12000) !Samples per 60 s
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real*4 dd(NMAX) !92 MB: raw data from Linrad timf2
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complex cx(NMAX/8) !Data at 1378.125 sps
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complex cx1(NMAX/8) !Data at 1378.125 sps, offset by 355.3 Hz
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complex c5x(NMAX/32) !Data at 344.53125 Hz
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complex c5a(512)
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real s2(66,126)
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real a(5)
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2018-03-05 14:49:51 -05:00
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logical bVHF,first,ljt65apon
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2018-02-08 21:28:33 -05:00
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character decoded*22,decoded_best*22
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character mycall*12,hiscall*12,hisgrid*6
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character*27 cr
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data first/.true./,jjjmin/1000/,jjjmax/-1000/,cr/'(C) 2016, Joe Taylor - K1JT'/
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save
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! Mix sync tone to baseband, low-pass filter, downsample to 1378.125 Hz
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call timer('filbig ',0)
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call filbig(dd,npts,f0,newdat,cx,n5,sq0)
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if(mode65.eq.4) call filbig(dd,npts,f0+355.297852,newdat,cx1,n5,sq0)
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call timer('filbig ',1)
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! NB: cx has sample rate 12000*77125/672000 = 1378.125 Hz
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! Check for a shorthand message
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if(bVHF .and. mode65.ne.101) then
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call sh65(cx,n5,mode65,ntol,xdf,nspecial,sync2)
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if(nspecial.gt.0) then
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a=0.
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a(1)=xdf
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nflip=0
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endif
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endif
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if(nflip.eq.0) go to 900
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! Find best DF, drift, curvature, and DT. Start by downsampling to 344.53125 Hz
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call timer('fil6521 ',0)
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call fil6521(cx,n5,c5x,n6)
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call timer('fil6521 ',1)
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fsample=1378.125/4.
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call timer('afc65b ',0)
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! Best fit for DF, drift, banana-coefficient, and dt. fsample = 344.53125 S/s
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dtbest=dt
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call afc65b(c5x,n6,fsample,nflip,a,ccfbest,dtbest)
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call timer('afc65b ',1)
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dtbest=dtbest+0.003628 !Remove decimation filter and coh. integrator delay
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dt=dtbest !Return new, improved estimate of dt
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sync2=3.7e-4*ccfbest/sq0 !Constant is empirical
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if(mode65.eq.4) cx=cx1
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! Apply AFC corrections to the time-domain signal
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! Now we are back to using the 1378.125 Hz sample rate, enough to
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! accommodate the full JT65C bandwidth.
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a(3)=0
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call timer('twkfreq ',0)
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call twkfreq65(cx,n5,a)
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call timer('twkfreq ',1)
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! Compute spectrum for each symbol.
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nsym=126
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nfft=512
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df=1378.125/nfft
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j=int(dtbest*1378.125)
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call timer('sh_ffts ',0)
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c5a=cmplx(0.0,0.0)
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do k=1,nsym
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do i=1,nfft
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j=j+1
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if(j.ge.1 .and. j.le.NMAX/8) then
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c5a(i)=cx(j)
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else
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c5a(i)=0.
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endif
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enddo
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call four2a(c5a,nfft,1,1,1)
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do i=1,512
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jj=i
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if(i.gt.256) jj=i-512
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s1(jj,k)=real(c5a(i))**2 + aimag(c5a(i))**2
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enddo
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enddo
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call timer('sh_ffts ',1)
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call timer('dec65b ',0)
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qualbest=0.
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qual0=-1.e30
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minsmo=0
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maxsmo=0
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if(mode65.ge.2 .and. mode65.ne.101) then
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minsmo=nint(width/df)-1
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maxsmo=2*nint(width/df)
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endif
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nn=0
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do ismo=minsmo,maxsmo
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if(ismo.gt.0) then
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do j=1,126
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call smo121(s1(-255,j),512)
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if(j.eq.1) nn=nn+1
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if(nn.ge.4) then
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call smo121(s1(-255,j),512)
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if(j.eq.1) nn=nn+1
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endif
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enddo
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endif
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do i=1,66
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jj=i
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if(mode65.eq.2) jj=2*i-1
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if(mode65.eq.4) then
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ff=4*(i-1)*df - 355.297852
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jj=nint(ff/df)+1
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endif
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s2(i,1:126)=s1(jj,1:126)
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enddo
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nadd=ismo !### ??? ###
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call decode65b(s2,nflip,nadd,mode65,ntrials,naggressive,ndepth, &
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2018-03-05 14:49:51 -05:00
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mycall,hiscall,hisgrid,nQSOProgress,ljt65apon,nexp_decode, &
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nqd,nft,qual, &
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nhist,decoded)
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2018-02-08 21:28:33 -05:00
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if(nft.eq.1) then
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nsmo=ismo
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param(9)=nsmo
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nsum=1
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exit
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else if(nft.eq.2) then
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if(qual.gt.qualbest) then
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decoded_best=decoded
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qualbest=qual
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nnbest=nn
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nsmobest=ismo
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endif
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endif
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if(qual.lt.qual0) exit
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qual0=qual
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enddo
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if(nft.eq.2) then
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decoded=decoded_best
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qual=qualbest
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nsmo=nsmobest
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param(9)=nsmo
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nn=nnbest
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endif
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call timer('dec65b ',1)
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900 return
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end subroutine decode65a
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