WSJT-X/spec441.f

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subroutine spec441(dat,jz,s,f0)
C Computes average spectrum over a range of dat, e.g. for a ping.
C Returns spectral array and frequency of peak value.
parameter (NFFT=256)
parameter (NR=NFFT+2)
parameter (NH=NFFT/2)
real*4 dat(jz)
real*4 x(NR),s(NH)
complex c(0:NH)
equivalence (x,c)
call zero(s,NH)
nz=jz/NFFT
do n=1,nz
j=1 + (n-1)*NFFT
call move(dat(j),x,NFFT)
call xfft(x,NFFT)
do i=1,NH
s(i)=s(i)+real(c(i))**2 + aimag(c(i))**2
enddo
enddo
smax=0.
df=11025.0/NFFT
fac=1.0/(100.0*nfft*nz)
do i=1,nh
s(i)=fac*s(i)
if(s(i).gt.smax) then
smax=s(i)
f0=i*df
endif
enddo
return
end