subroutine mskrtd(id2,nutc0,tsec,ntol,nrxfreq,ndepth,mycall,hiscall, & bshmsg,line) ! Real-time decoder for MSK144. ! Analysis block size = NZ = 7168 samples, t_block = 0.597333 s ! Called from hspec() at half-block increments, about 0.3 s parameter (NZ=7168) !Block size parameter (NSPM=864) !Number of samples per message frame parameter (NFFT1=8192) !FFT size for making analytic signal parameter (NPATTERNS=4) !Number of frame averaging patterns to try character*3 decsym !"&" for mskspd or "^" for long averages character*22 msgreceived !Decoded message character*22 msglast !!! temporary - used for dupechecking character*80 line !Formatted line with UTC dB T Freq Msg character*12 mycall,hiscall complex cdat(NFFT1) !Analytic signal complex c(NSPM) !Coherently averaged complex data complex ct(NSPM) integer*2 id2(NZ) !Raw 16-bit data integer iavmask(8) integer iavpatterns(8,NPATTERNS) integer npkloc(10) real d(NFFT1) real pow(8) real xmc(NPATTERNS) logical*1 bshmsg logical first data first/.true./ data iavpatterns/ & 1,1,1,1,0,0,0,0, & 0,0,1,1,1,1,0,0, & 1,1,1,1,1,0,0,0, & 1,1,1,1,1,1,1,0/ data xmc/2.0,4.5,2.5,3.5/ !Used to set time at center of averaging mask save first,tsec0,nutc00,pnoise,nsnrlast,msglast,cdat if(first) then tsec0=tsec nutc00=nutc0 pnoise=-1.0 first=.false. endif fc=nrxfreq !!! Dupe checking should probaby be moved to mainwindow.cpp if(nutc00.ne.nutc0 .or. tsec.lt.tsec0) then ! reset dupe checker msglast=' ' nsnrlast=-99 nutc00=nutc0 endif tframe=float(NSPM)/12000.0 line=char(0) msgreceived=' ' max_iterations=10 niterations=0 d(1:NZ)=id2 rms=sqrt(sum(d(1:NZ)*d(1:NZ))/NZ) if(rms.lt.1.0) go to 999 fac=1.0/rms d(1:NZ)=fac*d(1:NZ) d(NZ+1:NFFT1)=0. call analytic(d,NZ,NFFT1,cdat) !Convert to analytic signal and filter ! Calculate average power for each frame and for the entire block. ! If decode is successful, largest power will be taken as signal+noise. ! If no decode, entire-block average will be used to update noise estimate. pmax=-99 do i=1,8 ib=(i-1)*NSPM+1 ie=ib+NSPM-1 pow(i)=real(dot_product(cdat(ib:ie),cdat(ib:ie)))*rms**2 pmax=max(pmax,pow(i)) enddo pavg=sum(pow)/8.0 if(tsec.lt.0.1) pavg=sum(pow(6:8))/3.0 ! Short ping decoder uses squared-signal spectrum to determine where to ! center a 3-frame analysis window and attempts to decode each of the ! 3 frames along with 2- and 3-frame averages. np=8*NSPM call msk144spd(cdat,np,ntol,nsuccess,msgreceived,fc,fest,tdec,navg) !############################################################ !##### hardwired for testing - need to bring in Sh box status if(nsuccess.eq.0 .and. bshmsg) then call msk40spd(cdat,np,ntol,mycall(1:6),hiscall(1:6),nsuccess, & msgreceived,fc,fest,tdec,navg) endif if( nsuccess .eq. 1 ) then tdec=tsec+tdec decsym=' & ' ipk=0 is=0 goto 900 endif ! If short ping decoder doesn't find a decode, ! Fast - short ping decoder only. ! Normal - try 4-frame averages ! Deep - try 4-, 5- and 7-frame averages. npat=NPATTERNS if( ndepth .eq. 1 ) npat=0 if( ndepth .eq. 2 ) npat=2 do iavg=1,npat iavmask=iavpatterns(1:8,iavg) navg=sum(iavmask) deltaf=10.0/real(navg) ! search increment for frequency sync npeaks=2 call msk144sync(cdat(1:8*NSPM),8,ntol,deltaf,iavmask,npeaks,fc, & fest,npkloc,nsyncsuccess,xmax,c) if( nsyncsuccess .eq. 0 ) cycle do ipk=1,npeaks do is=1,3 ic0=npkloc(ipk) if(is.eq.2) ic0=max(1,ic0-1) if(is.eq.3) ic0=min(NSPM,ic0+1) ct=cshift(c,ic0-1) call msk144decodeframe(ct,msgreceived,ndecodesuccess) if(ndecodesuccess .gt. 0) then tdec=tsec+xmc(iavg)*tframe decsym=' & ' goto 900 endif enddo !Slicer dither enddo !Peak loop enddo msgreceived=' ' ! no decode - update noise level used for calculating displayed snr. if( pnoise .lt. 0 ) then ! initialize noise level pnoise=pavg elseif( pavg .gt. pnoise ) then ! noise level is slow to rise pnoise=0.9*pnoise+0.1*pavg elseif( pavg .lt. pnoise ) then ! and quick to fall pnoise=pavg endif go to 999 900 continue ! Successful decode - estimate snr !!! noise estimate needs work if( pnoise .gt. 0.0 ) then snr0=10.0*log10(pmax/pnoise-1.0) else snr0=0.0 endif nsnr=nint(snr0) !!!! Temporary - dupe check. Only print if new message, or higher snr. if(msgreceived.ne.msglast .or. nsnr.gt.nsnrlast .or. tsec.lt.tsec0) then msglast=msgreceived nsnrlast=nsnr if( nsnr .lt. -8 ) nsnr=-8 if( nsnr .gt. 24 ) nsnr=24 write(line,1020) nutc0,nsnr,tdec,nint(fest),decsym,msgreceived, & navg,char(0) 1020 format(i6.6,i4,f5.1,i5,a3,a22,i2,a1) endif 999 tsec0=tsec return end subroutine mskrtd