WSJT-X/lib/hspec.f90

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subroutine hspec(id2,k,nutc0,ntrpdepth,nrxfreq,ntol,bmsk144,ingain, &
green,s,jh,line1)
! Input:
! k pointer to the most recent new data
! nutc0 UTC for display of decode(s)
! ntrpdepth TR period and 1000*ndepth
! nrxfreq Rx audio center frequency
! ntol Decoding range is +/- ntol
! bmsk144 Boolean, true if in MSK144 mode
! ingain Relative gain for spectra
! Output:
! green() power
! s() spectrum for horizontal spectrogram
! jh index of most recent data in green(), s()
parameter (JZ=703)
character*80 line1
integer*2 id2(0:120*12000-1)
logical*1 bmsk144
real green(0:JZ-1)
real s(0:63,0:JZ-1)
real x(512)
complex cx(0:256)
data rms/999.0/,k0/99999999/
equivalence (x,cx)
save ja,rms0
ndepth=ntrpdepth/1000
ntrperiod=ntrpdepth - 1000*ndepth
gain=10.0**(0.1*ingain)
nfft=512
nstep=nfft
nblks=7
if(ntrperiod.lt.30) then
nstep=256
nblks=14
endif
if(k.gt.30*12000) go to 900
if(k.lt.nfft) then
jh=0
go to 900 !Wait for enough samples to start
endif
if(k.lt.k0) then !Start a new data block
ja=-nstep
jh=-1
rms0=0.0
endif
do iblk=1,nblks
if(jh.lt.JZ-1) jh=jh+1
ja=ja+nstep
jb=ja+nfft-1
x=id2(ja:jb)
sq=dot_product(x,x)
rms=sqrt(gain*sq/nfft)
green(jh)=0.
if(rms.gt.0.0) green(jh)=20.0*log10(rms)
call four2a(x,nfft,1,-1,0) !Real-to-complex FFT
df=12000.0/nfft
fac=(1.0/nfft)**2
do i=1,64
j=2*i
sx=real(cx(j))**2 + aimag(cx(j))**2 + real(cx(j-1))**2 + &
aimag(cx(j-1))**2
s(i-1,jh)=fac*gain*sx
enddo
if(ja+2*nfft.gt.k) exit
enddo
k0=k
if(bmsk144) then
if(k.ge.7168) then
tsec=(k-7168)/12000.0
call mskrtd(id2(k-7168+1:k),nutc0,tsec,ntol,nrxfreq,ndepth,line1)
endif
endif
900 return
end subroutine hspec