subroutine wspr_downsample(id2,k) ! Input: ! id2 raw 16-bit integer data, 12000 Hz sample rate ! k pointer to the most recent new data ! Output (in common/c0com) ! c0 complex data downsampled to 1500 Hz parameter (NMAX=120*12000) !Total sample intervals per 30 minutes parameter (NDMAX=120*1500) !Sample intervals at 1500 Hz rate parameter (NSMAX=1366) !Max length of saved spectra parameter (NFFT1=1024) parameter (MAXFFT3=32768) real*4 w3(MAXFFT3) real*4 x0(NFFT1),x1(NFFT1) real*4 x2(NFFT1+105) real*4 ssum(NSMAX) logical*1 lstrong(0:1023) !Should be (0:512) integer*2 id2(NMAX) complex c0 common/c0com/c0(NDMAX) data rms/999.0/,k0/99999999/,nfft3z/0/,nsps/8192/,nbfo/1500/ save nfft3=nsps/4 jstep=nsps/16 if(k.gt.NMAX) go to 999 if(k.lt.nfft3) go to 999 !Wait for enough samples to start if(nfft3.ne.nfft3z) then pi=4.0*atan(1.0) do i=1,nfft3 w3(i)=2.0*(sin(i*pi/nfft3))**2 !Window for nfft3 enddo nfft3z=nfft3 endif if(k.lt.k0) then ja=0 ssum=0. k1=0 k8=0 x2=0. ! if(ndiskdat.eq.0) then ! id2(k+1:)=0 ! c0=0. !This is necessary to prevent "ghosts". Not sure why. ! endif endif k0=k nzap=0 nbslider=0 sigmas=1.0*(10.0**(0.01*nbslider)) + 0.7 peaklimit=sigmas*max(10.0,rms) px=0. nwindow=2 kstep1=NFFT1 if(nwindow.ne.0) kstep1=NFFT1/2 fac=2.0/NFFT1 nblks=(k-k1)/kstep1 gain=1.0 nb=0 do nblk=1,nblks do i=1,NFFT1 x0(i)=gain*id2(k1+i) enddo ! call timf2(x0,k,NFFT1,nwindow,nb,peaklimit,x1, & ! slimit,lstrong,px,nzap) ! Mix at nbfo Hz, lowpass at +/-750 Hz, and downsample to 1500 Hz complex. call mixlpf(x0,nbfo,c0(k8+1)) k1=k1+kstep1 k8=k8+kstep1/8 enddo 999 return end subroutine wspr_downsample