WSJT-X/lib/fsk4hf/getfc1w.f90

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subroutine getfc1w(c,fs,fa,fb,fc1,xsnr)
include 'wsprlf_params.f90'
complex c(0:NZ-1) !Complex waveform
complex c2(0:NFFT1-1) !Short spectra
real s(-NH1+1:NH1) !Coarse spectrum
nspec=NZ/NFFT1
df1=fs/NFFT1
s=0.
do k=1,nspec
ia=(k-1)*N2
ib=ia+N2-1
c2(0:N2-1)=c(ia:ib)
c2(N2:)=0.
call four2a(c2,NFFT1,1,-1,1)
do i=0,NFFT1-1
j=i
if(j.gt.NH1) j=j-NFFT1
s(j)=s(j) + real(c2(i))**2 + aimag(c2(i))**2
enddo
enddo
! call smo121(s,NFFT1)
smax=0.
ipk=0
fc1=0.
ia=nint(fa/df1)
ib=nint(fb/df1)
do i=ia,ib
f=i*df1
if(s(i).gt.smax) then
smax=s(i)
ipk=i
fc1=f
endif
! write(51,3001) f,s(i),db(s(i))
! 3001 format(f10.3,e12.3,f10.3)
enddo
! The following is for testing SNR calibration:
sp3n=(s(ipk-1)+s(ipk)+s(ipk+1)) !Sig + 3*noise
base=(sum(s)-sp3n)/(NFFT1-3.0) !Noise per bin
psig=sp3n-3*base !Sig only
pnoise=(2500.0/df1)*base !Noise in 2500 Hz
xsnr=db(psig/pnoise)
return
end subroutine getfc1w