WSJT-X/libm65/symspecx.f90

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subroutine symspecx(k,nsps,ndiskdat,nb,nbslider,pxdb,s,nkhz,ihsym, &
nzap,slimit,lstrong)
! k pointer to the most recent new data
! nsps samples per symbol (at 12000 Hz)
! ndiskdat 0/1 to indicate if data from disk
! nb 0/1 status of noise blanker (off/on)
! pxdb power (0-60 dB)
! s spectrum for waterfall display
! nkhz integer kHz portion of center frequency, e.g., 125 for 144.125
! ihsym index number of this half-symbol (1-322)
! nzap number of samples zero'ed by noise blanker
parameter (NMAX=1800*12000) !Total sample intervals per 30 minutes
parameter (NSMAX=4400) !Max length of saved spectra
parameter (MAXFFT=262144) !Max length of FFTs
integer*2 id2
real*8 ts,hsym
real*8 fcenter
common/jt8com/id2(NMAX),ss(184,NSMAX),savg(NSMAX),fcenter,nutc,junk(20)
real*4 s(NSMAX)
real x(MAXFFT)
complex cx(0:MAXFFT/2)
equivalence (x,cx)
data rms/999.0/,k0/99999999/,ntrperiod0/0/
save
nfft=nsps
hsym=nsps/2
if(k.gt.NMAX) go to 999
if(k.lt.nfft) then
ihsym=0
go to 999 !Wait for enough samples to start
endif
if(k.lt.k0) then
ts=1.d0 - hsym
savg=0.
ihsym=0
k1=0
if(ndiskdat.eq.0) id2(k+1)=0. !### Should not be needed ??? ###
endif
k0=k
nzap=0
sigmas=1.5*(10.0**(0.01*nbslider)) + 0.7
peaklimit=sigmas*max(10.0,rms)
faclim=3.0
ts=ts+hsym
ja=ts !Index of first sample
jb=ja+nfft-1 !Last sample
i=0
sq=0.
do j=ja,jb !Copy data into cx, cy
i=i+1
x(i)=id2(j)
sq=sq + x(i)*x(i)
enddo
rms=sqrt(sq/nfft)
pxdb=0.
if(rms.gt.1.0) pxdb=20.0*log10(rms)
if(pxdb.gt.60.0) pxdb=60.0
ihsym=ihsym+1
call four2a(x,nfft,1,-1,0) !Forward FFT of symbol length
df=12000.0/nfft
nzh=min(nint(500.0/df),2200)
nz=2*nzh
i0=nint(1500.0/df) - nzh
rewind 71
do i=1,nz
sx=real(cx(i0+i))**2 + aimag(cx(i0+i))**2
sx=1.e-8*sx
s(i)=sx
savg(i)=savg(i) + sx
if(ihsym.le.184) ss(ihsym,i)=sx
write(71,3001) (i0+i-1)*df,savg(i),db(savg(i))
3001 format(f12.6,2f12.3)
enddo
flush(71)
nkhz=100
999 return
end subroutine symspecx