mirror of https://github.com/saitohirga/WSJT-X.git
107 lines
3.3 KiB
Fortran
107 lines
3.3 KiB
Fortran
subroutine stdecode(s2,nchan,nz,sigma,dtbuf,df,stlim0,
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+ DFTolerance,cfile6,pick,istart)
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C Search for and decode single-tone messages.
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real s2(nchan,nz)
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integer DFTolerance
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logical pick
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character cfile6*6,msg3*3
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character*90 line
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common/ccom/nline,tping(100),line(100)
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NSPD=25 !Change if FSK110 is implemented
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LTone=2
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NBaud=11025/NSPD
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stlim=stlim0
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if(pick) stlim=stlim0-1.0
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iwidth=1
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ts0=-1.0
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dt=1.0/11025.0
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C In each time slice, find largest peak between LTone*NBaud-DFTolerance and
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C (LTone+3)*NBaud+DFTolerance.
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ia=(LTone*NBaud-DFTolerance)/df - 5.0
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ib=((LTone+3)*NBaud+DFTolerance)/df - 4.0
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do j=1,nz
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smax=0.
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do i=ia,ib !Get the spectral peak
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if(s2(i,j).gt.smax) then
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smax=s2(i,j)
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ipk=i
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endif
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enddo
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peak=dB(smax/sigma) - 14.0 !Empirical
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C constant should be dB(43/2500) = -17.6 dB?
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if(peak.gt.stlim) then
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C To minimize false ST decodings from QRN and MT pings, find the
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C second best peak (excluding points around the first peak).
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smax2=0.
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do i=ia,ib
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if((abs(i-ipk).gt.iwidth) .and. s2(i,j).gt.smax2) then
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smax2=s2(i,j)
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ipk2=i
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endif
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enddo
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C Larger values of ratlim make it more likely to report ST decodings.
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ratlim=0.18
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if(stlim.lt.-2.5) ratlim=0.20
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if(stlim.lt.-3.5) ratlim=0.22
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if(stlim.lt.-4.5) ratlim=0.24
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if(pick) ratlim=0.27 !Fine tuning here...
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if(smax2/smax.gt.ratlim) goto 20
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call peakup(s2(ipk-1,j),s2(ipk,j),s2(ipk+1,j),dx)
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freq=(ipk+5+dx)*df
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tstart=j*dtbuf + dt*(istart-1)
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mswidth=20
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nwidth=0
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nstrength=0
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n=nint(freq/NBaud)
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noffset=freq-n*NBaud
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if((noffset.lt.-DFTolerance) .or.
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+ (noffset.gt.DFTolerance)) goto 20
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C The numbers 2 and 5 depend on Ltone:
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if(n.lt.2 .or. n.gt.5) goto 20
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C OK, this detection has survived all tests. Save it for output
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C (uness perhaps it is redundant).
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if(n.eq.LTone) msg3='R26'
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if(n.eq.LTone+1) msg3='R27'
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if(n.eq.LTone+2) msg3='RRR'
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if(n.eq.LTone+3) msg3='73'
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C Now check for redundant detections. (Not sure, now, why I chose
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C the time span 0.11 s.)
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if(tstart-ts0.gt.0.11) then
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peak0=0. !If time diff>0.11s, start fresh
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else
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if(peak.le.peak0) goto 20
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nline=nline-1 !Delete previous, this one's better
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peak0=peak !Save best peak
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endif
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C OK, we want to output this one. Save the information.
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if(nline.le.99) nline=nline+1
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ts0=tstart
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tping(nline)=tstart
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nst=(int(smax/smax2)-4)/2 + 1
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if(nst.lt.1) nst=1
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if(nst.gt.3) nst=3
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write(line(nline),1050) cfile6,tstart,mswidth,int(peak),
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+ nwidth,nstrength,noffset,msg3,nst
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1050 format(a6,f5.1,i5,i3,1x,2i1,i5,1x,a3,40x,i3)
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endif
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20 continue
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enddo
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return
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end
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