mirror of https://github.com/saitohirga/WSJT-X.git
225 lines
6.0 KiB
Fortran
225 lines
6.0 KiB
Fortran
subroutine q65_sync(iwave,nmax,mode_q65,nQSOprogress,nsps,nfqso,ntol, &
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xdt,f0,snr1,dat4,snr2,irc)
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! Detect and align with the Q65 sync vector, returning time and frequency
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! offsets and SNR estimate.
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! Input: iwave(0:nmax-1) Raw data
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! mode_q65 Tone spacing 1 2 4 8 16 (A-E)
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! nsps Samples per symbol at 12000 Sa/s
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! nfqso Target frequency (Hz)
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! ntol Search range around nfqso (Hz)
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! Output: xdt Time offset from nominal (s)
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! f0 Frequency of sync tone
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! snr1 Relative SNR of sync signal
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parameter (NSTEP=8) !Step size nsps/NSTEP
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parameter (LN=2176*63) !LN=LL*NN; LL=64*(mode_q65+2), NN=63
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character*37 msg,msgsent
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integer*2 iwave(0:nmax-1) !Raw data
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integer isync(22) !Indices of sync symbols
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integer itone(85)
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integer codewords(63,64)
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integer dat4(13)
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integer ijpk(2)
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real, allocatable :: s1(:,:) !Symbol spectra, 1/8-symbol steps
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real, allocatable :: s3(:,:) !Data-symbol energies s3(LL,63)
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real, allocatable :: ccf(:,:) !CCF(freq,lag)
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real, allocatable :: ccf1(:) !CCF(freq) at best lag
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real s3prob(0:63,63) !Symbol-value probabilities
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real sync(85) !sync vector
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complex, allocatable :: c0(:) !Complex spectrum of symbol
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data isync/1,9,12,13,15,22,23,26,27,33,35,38,46,50,55,60,62,66,69,74,76,85/
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data sync(1)/99.0/
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save sync
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LL=64*(2+mode_q65)
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nfft=nsps
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df=12000.0/nfft !Freq resolution = baud
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istep=nsps/NSTEP
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iz=5000.0/df !Uppermost frequency bin, at 5000 Hz
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txt=85.0*nsps/12000.0
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jz=(txt+1.0)*12000.0/istep !Number of quarter-symbol steps
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if(nsps.ge.6912) jz=(txt+2.0)*12000.0/istep !For TR 60 s and higher
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ia=ntol/df
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allocate(s1(iz,jz))
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allocate(s3(-64:LL-65,63))
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allocate(c0(0:nfft-1))
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allocate(ccf(-ia:ia,-53:214))
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allocate(ccf1(-ia:ia))
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if(sync(1).eq.99.0) then !Generate the sync vector
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sync=-22.0/63.0 !Sync tone OFF
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do k=1,22
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sync(isync(k))=1.0 !Sync tone ON
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enddo
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endif
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fac=1/32767.0
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do j=1,jz !Compute symbol spectra at step size
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ia=(j-1)*istep
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ib=ia+nsps-1
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k=-1
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do i=ia,ib,2 !Load iwave data into complex array c0, for r2c FFT
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xx=iwave(i)
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yy=iwave(i+1)
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k=k+1
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c0(k)=fac*cmplx(xx,yy)
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enddo
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c0(k+1:)=0.
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call four2a(c0,nfft,1,-1,0) !r2c FFT
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do i=1,iz
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s1(i,j)=real(c0(i))**2 + aimag(c0(i))**2
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enddo
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! For large Doppler spreads, should we smooth the spectra here?
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! call smo121(s1(1:iz,j),iz)
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enddo
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i0=nint(nfqso/df) !Target QSO frequency
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call pctile(s1(i0-64:i0+192,1:jz),129*jz,40,base)
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! s1=s1/base - 1.0
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s1=s1/base
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! Apply fast AGC
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s1max=20.0 !Empirical choice
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do j=1,jz
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smax=maxval(s1(i0-64:i0+192,j))
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if(smax.gt.s1max) s1(i0-64:i0+192,j)=s1(i0-64:i0+192,j)*s1max/smax
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enddo
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dtstep=nsps/(NSTEP*12000.0) !Step size in seconds
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ia=ntol/df
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lag1=-1.0/dtstep
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lag2=1.0/dtstep + 0.9999
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j0=0.5/dtstep
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if(nsps.ge.6192) then
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j0=1.0/dtstep !Nominal index for start of signal
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lag2=4.0/dtstep + 0.9999 !Include EME delays
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endif
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ccf=0.
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do lag=lag1,lag2
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do k=1,85
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n=NSTEP*(k-1) + 1
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j=n+lag+j0
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if(j.ge.1 .and. j.le.jz) then
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ccf(-ia:ia,lag)=ccf(-ia:ia,lag) + sync(k)*s1(i0-ia:i0+ia,j)
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endif
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enddo
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enddo
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ijpk=maxloc(ccf)
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ipk=ijpk(1)-ia-1
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jpk=ijpk(2)-53-1
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f0=nfqso + ipk*df
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xdt=jpk*dtstep
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sq=0.
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nsq=0
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do j=lag1,lag2
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if(abs(j-jpk).gt.6) then
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sq=sq + ccf(ipk,j)**2
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nsq=nsq+1
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endif
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enddo
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rms=sqrt(sq/nsq)
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smax=ccf(ipk,jpk)
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snr1=smax/rms
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!######################################################################
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! Experimental: Try early list decoding via "Deep Likelihood".
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if(nQSOprogress.lt.1) go to 900
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snr1a_best=0.
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do imsg=1,4
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ccf=0.
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msg='K1ABC W9XYZ RRR'
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if(imsg.eq.2) msg='K1ABC W9XYZ RR73'
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if(imsg.eq.3) msg='K1ABC W9XYZ 73'
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if(imsg.eq.4) msg='CQ K9AN EN50'
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call genq65(msg,0,msgsent,itone,i3,n3)
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j=0
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do k=1,85
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if(sync(k)>0.) cycle
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j=j+1
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codewords(j,imsg)=itone(k) - 1
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enddo
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! Compute 2D ccf using all 85 symbols in the list message
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do lag=lag1,lag2
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do k=1,85
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j=j0 + NSTEP*(k-1) + 1 + lag
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if(j.ge.1 .and. j.le.jz) then
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do i=-ia,ia
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ii=i0+itone(k)+i
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ccf(i,lag)=ccf(i,lag) + s1(ii,j)
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enddo
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endif
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enddo
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enddo
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ijpk=maxloc(ccf)
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ipk=ijpk(1)-ia-1
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jpk=ijpk(2)-53-1
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f0a=nfqso + ipk*df
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xdta=jpk*dtstep
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sq=0.
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nsq=0
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do j=lag1,lag2
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if(abs(j-jpk).gt.6) then
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sq=sq + ccf(ipk,j)**2
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nsq=nsq+1
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endif
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enddo
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rms=sqrt(sq/nsq)
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smax=ccf(ipk,jpk)
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snr1a=smax/rms
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if(snr1a.gt.snr1a_best) then
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snr1a_best=snr1a
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imsg_best=imsg
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xdta_best=xdta
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f0a_best=f0a
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endif
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enddo ! imsg
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if(snr1a_best.gt.2.0) then
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xdt=xdta_best
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f0=f0a_best
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snr1=1.4*snr1a_best
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endif
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ia=i0+ipk-63
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ib=ia+LL-1
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j=j0+jpk-5
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n=0
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do k=1,85
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j=j+8
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if(sync(k).gt.0.0) then
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cycle
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endif
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n=n+1
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s3(-64:LL-65,n)=s1(ia:ib,j)
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enddo
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nsubmode=0
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nFadingModel=1
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baud=12000.0/nsps
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dat4=0
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irc=-2
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do ibw=0,10
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b90=1.72**ibw
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call q65_intrinsics_ff(s3,nsubmode,b90/baud,nFadingModel,s3prob)
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call q65_dec_fullaplist(s3,s3prob,codewords,4,esnodb,dat4,plog,irc)
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if(irc.ge.0) then
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xdt=xdta_best
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f0=f0a_best
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snr2=esnodb - db(2500.0/baud)
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exit
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endif
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enddo
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900 return
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end subroutine q65_sync
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