mirror of https://github.com/saitohirga/WSJT-X.git
76 lines
1.5 KiB
Fortran
76 lines
1.5 KiB
Fortran
subroutine mskdf(cdat,npts,t2,nfft1,f0,nfreeze,mousedf,ntol,dfx,snrsq2)
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! Determine DF for a JTMS signal. Also find ferr, a measure of
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! frequency differerence between 1st and 2nd harmonic.
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! (Should be 0.000)
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parameter (NZ=128*1024)
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complex cdat(npts)
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integer ntol
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real sq(NZ)
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real ccf(-2600:2600) !Correct limits?
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real tmp(NZ)
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complex c(NZ)
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data nsps/8/
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save c
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df1=48000.0/nfft1
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nh=nfft1/2
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fac=1.0/(nfft1**2)
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do i=1,npts
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c(i)=fac*cdat(i)**2
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enddo
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c(npts+1:nfft1)=0.
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call four2a(c,nfft1,1,-1,1)
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! In the "doubled-frequencies" spectrum of squared cdat:
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fa=2.0*(f0-400)
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fb=2.0*(f0+400)
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j0=nint(2.0*f0/df1)
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ja=nint(fa/df1)
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jb=nint(fb/df1)
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jd=nfft1/nsps
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do j=1,nh+1
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sq(j)=real(c(j))**2 + aimag(c(j))**2
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! if(j*df1.lt.6000.0) write(54,3009) j*df1,sq(j),db(sq(j))
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!3009 format(3f12.3)
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enddo
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ccf=0.
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do j=ja,jb
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ccf(j-j0-1)=sq(j)+sq(j+jd)
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enddo
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call pctile(ccf(ja-j0-1),tmp,jb-ja+1,50,base)
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ccf=ccf/base
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if(NFreeze.gt.0) then
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fa=2.0*(f0+MouseDF-ntol)
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fb=2.0*(f0+MouseDF+ntol)
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endif
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ja=nint(fa/df1)
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jb=nint(fb/df1)
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! rewind 51
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smax=0.
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do j=ja,jb
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k=j-j0-1
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if(ccf(k).gt.smax) then
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smax=ccf(k)
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jpk=j
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endif
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f=0.5*k*df1
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! write(51,3002) f,ccf(k)
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!3002 format(2f12.3)
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enddo
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! call flush(51)
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fpk=(jpk-1)*df1
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dfx=0.5*fpk-f0
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snrsq2=smax
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return
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end subroutine mskdf
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