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Improve sensitivity of msk32 decoder.
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6885 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
This commit is contained in:
Steven Franke
parent
ea3ec805ab
commit
b9a6d346b5
@ -319,98 +319,103 @@ subroutine detectmsk32(cbig,n,lines,nmessages,nutc)
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cca=sum(c(1:1+41)*conjg(cb))
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phase0=atan2(imag(cca),real(cca))
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! Remove phase error - want constellation rotated so that sample points lie on I/Q axes
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cfac=cmplx(cos(phase0),sin(phase0))
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c=c*conjg(cfac)
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do ipha=1,3
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if( ipha.eq.2 ) phase0=phase0-20*pi/180.0
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if( ipha.eq.3 ) phase0=phase0+20*pi/180.0
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if( nmatchedfilter .eq. 0 ) then
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! Remove phase error - want constellation rotated so that sample points lie on I/Q axes
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cfac=cmplx(cos(phase0),sin(phase0))
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c=c*conjg(cfac)
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if( nmatchedfilter .eq. 0 ) then
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! sample to get softsamples
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do i=1, 16
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softbits(2*i-1)=imag(c(1+(i-1)*12))
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softbits(2*i)=real(c(7+(i-1)*12))
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enddo
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else
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do i=1, 16
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softbits(2*i-1)=imag(c(1+(i-1)*12))
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softbits(2*i)=real(c(7+(i-1)*12))
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enddo
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else
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! matched filter -
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softbits(1)=sum(imag(c(1:6))*pp(7:12))+sum(imag(c(NSPM-5:NSPM))*pp(1:6))
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softbits(2)=sum(real(c(1:12))*pp)
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do i=2,16
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softbits(2*i-1)=sum(imag(c(1+(i-1)*12-6:1+(i-1)*12+5))*pp)
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softbits(2*i)=sum(real(c(7+(i-1)*12-6:7+(i-1)*12+5))*pp)
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enddo
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endif
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softbits(1)=sum(imag(c(1:6))*pp(7:12))+sum(imag(c(NSPM-5:NSPM))*pp(1:6))
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softbits(2)=sum(real(c(1:12))*pp)
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do i=2,16
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softbits(2*i-1)=sum(imag(c(1+(i-1)*12-6:1+(i-1)*12+5))*pp)
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softbits(2*i)=sum(real(c(7+(i-1)*12-6:7+(i-1)*12+5))*pp)
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enddo
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endif
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! sync word hard error weight is a good discriminator for
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! frames that have reasonable probability of decoding
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hardbits=0
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do i=1, 32
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if( softbits(i) .ge. 0.0 ) then
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hardbits(i)=1
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endif
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enddo
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nbadsync1=(8-sum( (2*hardbits(1:8)-1)*s8r ) )/2
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nbadsync=nbadsync1
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if( nbadsync .gt. 3 ) cycle
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hardbits=0
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do i=1, 32
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if( softbits(i) .ge. 0.0 ) then
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hardbits(i)=1
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endif
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enddo
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nbadsync1=(8-sum( (2*hardbits(1:8)-1)*s8r ) )/2
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nbadsync=nbadsync1
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if( nbadsync .gt. 3 ) cycle
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! normalize the softsymbols before submitting to decoder
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sav=sum(softbits)/32
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s2av=sum(softbits*softbits)/32
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ssig=sqrt(s2av-sav*sav)
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softbits=softbits/ssig
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sav=sum(softbits)/32
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s2av=sum(softbits*softbits)/32
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ssig=sqrt(s2av-sav*sav)
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softbits=softbits/ssig
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if( qsocontext ) then
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if( qsocontext ) then
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! search 32 likely messages only, using correlation discrepancy
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cd=1e6
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ihammd=99
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do i=0,31
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ncw=ig24(likelymessages(i))
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cd(i)=0.0
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ihammd(i)=0
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do ii=1,24
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ib=iand(1,ishft(ncw,1-ii))
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ib=2*ib-1
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if( ib*softbits(ii+8) .lt. 0 ) cd(i)=cd(i)+abs(softbits(ii+8))
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if( ib*(2*hardbits(ii+8)-1) .lt. 0 ) ihammd(i)=ihammd(i)+1
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cd=1e6
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ihammd=99
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do i=0,31
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ncw=ig24(likelymessages(i))
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cd(i)=0.0
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ihammd(i)=0
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do ii=1,24
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ib=iand(1,ishft(ncw,1-ii))
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ib=2*ib-1
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if( ib*softbits(ii+8) .lt. 0 ) cd(i)=cd(i)+abs(softbits(ii+8))
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if( ib*(2*hardbits(ii+8)-1) .lt. 0 ) ihammd(i)=ihammd(i)+1
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enddo
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enddo
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enddo
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else
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else
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! exhaustive search decoder, using correlation discrepancy
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cd=1e6
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ihammd=99
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do i=0,4096-1
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ncw=ig24(i)
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cd(i)=0.0
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ihammd(i)=0
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do ii=1,24
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ib=iand(1,ishft(ncw,1-ii))
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ib=2*ib-1
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if( ib*softbits(ii+8) .lt. 0 ) cd(i)=cd(i)+abs(softbits(ii+8))
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if( ib*(2*hardbits(ii+8)-1) .lt. 0 ) ihammd(i)=ihammd(i)+1
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cd=1e6
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ihammd=99
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do i=0,4096-1
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ncw=ig24(i)
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cd(i)=0.0
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ihammd(i)=0
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do ii=1,24
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ib=iand(1,ishft(ncw,1-ii))
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ib=2*ib-1
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if( ib*softbits(ii+8) .lt. 0 ) cd(i)=cd(i)+abs(softbits(ii+8))
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if( ib*(2*hardbits(ii+8)-1) .lt. 0 ) ihammd(i)=ihammd(i)+1
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enddo
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enddo
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enddo
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endif
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cdm=minval(cd)
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iloc=minloc(cd)
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imsg=iloc(1)-1
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cd(imsg)=1e6
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cdm2=minval(cd)
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iloc=minloc(cd)
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imsg2=iloc(1)-1
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cdrat=cdm2/(cdm+0.001)
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! if( cdrat .gt. cdratbest ) then
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if( cdm .lt. cdbest ) then
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cdratbest = cdrat
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cdbest = cdm
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imsgbest = imsg
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iavbest = iav
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ipbest = ip
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ipkbest = ipk
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idfbest = idf
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idbest = id
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nbadsyncbest = nbadsync
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if( ( ihammd(imsgbest)+nbadsyncbest .le. 4 ) .and. ( (cdratbest .gt. 100.0) .and. (cdbest .le. 0.05) ) ) goto 999
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endif
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endif
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cdm=minval(cd)
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iloc=minloc(cd)
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imsg=iloc(1)-1
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cd(imsg)=1e6
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cdm2=minval(cd)
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iloc=minloc(cd)
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imsg2=iloc(1)-1
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cdrat=cdm2/(cdm+0.001)
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! if( cdrat .gt. cdratbest ) then
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if( cdm .lt. cdbest ) then
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cdratbest = cdrat
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cdbest = cdm
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imsgbest = imsg
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iavbest = iav
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ipbest = ip
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ipkbest = ipk
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idfbest = idf
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idbest = id
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iphabest = ipha
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nbadsyncbest = nbadsync
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if( ( ihammd(imsgbest)+nbadsyncbest .le. 4 ) .and. ( (cdratbest .gt. 100.0) .and. (cdbest .le. 0.05) ) ) goto 999
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endif
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enddo ! phase loop
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enddo ! frame averaging loop
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enddo ! frequency dithering loop
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enddo ! sample-time dither loop
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@ -441,9 +446,9 @@ subroutine detectmsk32(cbig,n,lines,nmessages,nutc)
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! write(*,1022) nutc,ipbest,times(ipbest),snrs(ipbest),fest,nrxrpt,nrxhash, &
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! rpt(nrxrpt),imessage,ig24(imessage),ihammd(imsgbest), &
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! cdbest,cdratbest,nbadsyncbest,ipkbest,idbest,idfbest,iavbest
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! cdbest,cdratbest,nbadsyncbest,ipkbest,idbest,idfbest,iavbest,iphabest
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endif
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endif
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!1022 format(i4.4,2x,i4,f8.3,f8.2,f8.2,i6,i6,a6,i8,i10,i4,f8.2,f8.2,i5,i5,i5,i5,i5)
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!1022 format(i4.4,2x,i4,f8.3,f8.2,f8.2,i6,i6,a6,i8,i10,i4,f8.2,f8.2,i5,i5,i5,i5,i5,i5)
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return
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end subroutine detectmsk32
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