Below is the lag spectrum (correlation function) produced when observing a strong calibrator in continuum (bandwidth 128MHz) mode with 32 channels. This function is the Fourier transform of the spectrum, so for a pure square wave type spectrum you expect a sinc function.
Below is the lag spectrum produced when observing a weak calibrator in spectral line (bandwidth 8MHz) mode using 1024 channels. This function is the Fourier transform of the spectrum, so for a pure square wave type spectrum you expect a very narrow sinc function.
![\begin{figure}
\centering
\includegraphics[width=0.3\textwidth]{lag_1.ps}
\end{figure}](img120.gif){kind=small}
![\begin{figure}
\centering
\includegraphics[width=0.3\textwidth]{lag_3.ps}
\end{figure}](img121.gif){kind=small}