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subroutine rectify_msk(c,msg0,imsg,freq2)
parameter (NSPM=1404)
complex c(0:NSPM-1) !Received data
complex cmsg(0:NSPM-1) !Message waveform
complex c1(0:NSPM-1) !Rectified signal
complex c2(0:NSPM-1) !Integral of rectified signal
complex c3(0:2*NSPM-1) !FFT of rectified signal
complex cfac
character*22 msg0,msg,msgsent
integer i4tone(234)
ichk=0
msg=msg0
nsym=234
if(imsg.ge.0) then
ichk=10000+imsg
msg="<C1ALL C2ALL> 73"
nsym=35
endif
call genmsk(msg,ichk,msgsent,i4tone,itype) !Get tone sequence for msg
twopi=8.0*atan(1.0)
dt=1.0/12000.0
f0=1000.0
f1=2000.0
phi=0.
dphi=0.
k=-1
c2=0.
do j=1,nsym !Generate Tx waveform for msg
if(i4tone(j).eq.0) dphi=twopi*f0*dt
if(i4tone(j).eq.1) dphi=twopi*f1*dt
do i=1,6
k=k+1
phi=phi+dphi
cmsg(k)=cmplx(cos(phi),sin(phi))
c1(k)=conjg(cmsg(k))*c(k)
if(k.ge.1) c2(k)=c2(k-1) + c1(k)
enddo
enddo
c2(0)=c2(1)
pha=atan2(aimag(c2(NSPM-1)),real(c2(NSPM-1)))
cfac=cmplx(cos(pha),-sin(pha))
c1=cfac*c1
c2=cfac*c2
nfft=2*NSPM
c3(0:NSPM-1)=c2
c3(NSPM:nfft-1)=0.
df=12000.0/nfft
call four2a(c3,nfft,1,-1,1)
smax=0.
do i=0,nfft-1
f=i*df
if(i.gt.nfft/2) f=f-12000.0
s=1.e-10*(real(c3(i))**2 + aimag(c3(i))**2)
if(s.gt.smax) then
smax=s
freq2=1500.0 + f
endif
enddo
return
end subroutine rectify_msk
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