subroutine decode65a(dd,npts,newdat,nqd,f0,nflip,mode65,ntrials, & naggressive,ndepth,sync2,a,dt,nsf,nhist,decoded) ! Apply AFC corrections to a candidate JT65 signal, then decode it. parameter (NMAX=60*12000) !Samples per 60 s real*4 dd(NMAX) !92 MB: raw data from Linrad timf2 complex cx(NMAX/8) !Data at 1378.125 samples/s complex c5x(NMAX/32) !Data at 344.53125 Hz complex c5a(512) real s2(66,126) real a(5) logical first character decoded*22 data first/.true./,jjjmin/1000/,jjjmax/-1000/ data nhz0/-9999999/ save ! Mix sync tone to baseband, low-pass filter, downsample to 1378.125 Hz call timer('filbig ',0) call filbig(dd,npts,f0,newdat,cx,n5,sq0) call timer('filbig ',1) ! NB: cx has sample rate 12000*77125/672000 = 1378.125 Hz ! Find best DF, drift, curvature, and DT. Start by downsampling to 344.53125 Hz call timer('fil6521 ',0) call fil6521(cx,n5,c5x,n6) call timer('fil6521 ',1) fsample=1378.125/4. call timer('afc65b ',0) ! Best fit for DF, drift, banana-coefficient, and dt. fsample = 344.53125 S/s dtbest=dt call afc65b(c5x,n6,fsample,nflip,a,ccfbest,dtbest) call timer('afc65b ',1) sync2=3.7e-4*ccfbest/sq0 !Constant is empirical ! Apply AFC corrections to the time-domain signal ! Now we are back to using the 1378.125 Hz sample rate, enough to ! accommodate the full JT65C bandwidth. a(3)=0 call timer('twkfreq ',0) call twkfreq65(cx,n5,a) call timer('twkfreq ',1) ! Compute spectrum for each symbol. nsym=126 nfft=512 j=int(dtbest*1378.125) if(j.lt.0) j=0 c5a=cmplx(0.0,0.0) call timer('sh_ffts ',0) do k=1,nsym do i=1,nfft j=j+1 if( j .le. NMAX/8 ) c5a(i)=cx(j) enddo call four2a(c5a,nfft,1,1,1) do i=1,66 jj=i if(mode65.eq.2) jj=2*i-1 if(mode65.eq.4) jj=4*i-3 s2(i,k)=real(c5a(jj))**2 + aimag(c5a(jj))**2 enddo enddo call timer('sh_ffts ',1) call timer('dec65b ',0) call decode65b(s2,nflip,mode65,ntrials,naggressive,ndepth,nqd,nsf, & nhist,decoded) dt=dtbest !return new, improved estimate of dt call timer('dec65b ',1) return end subroutine decode65a