subroutine peakdf9(c0,npts8,nsps8,istart,foffset,xdf)

  complex c0(0:npts8-1)
  complex zsum
  integer ii(16)                       !Locations of sync symbols
  data ii/1,6,11,16,21,26,31,39,45,51,57,63,69,75,81,85/

  twopi=8.0*atan(1.0)
  df=1500.0/nsps8
  smax=0.
  do idf=-10,10
     f0=foffset + 0.1*df*idf
     dphi=twopi*f0/1500.0
     sum=0.
     do j=1,16
        i1=(ii(j)-1)*nsps8 + istart
        phi=0.
        zsum=0.
        do i=i1,i1+nsps8-1
           if(i.lt.0) cycle
           phi=phi + dphi
           zsum=zsum + c0(i) * cmplx(cos(phi),-sin(phi))
        enddo
        sum=sum + real(zsum)**2 + aimag(zsum)**2
     enddo
     if(sum.gt.smax) then
        idfpk=idf
        fpk=f0
        smax=sum
     endif
  enddo

  write(*,3001) idfpk,fpk,smax
3001 format('DF:'i5,f8.2,f12.3)

  return
end subroutine peakdf9