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Recognising early/normal problems

A poor early/normal calibration will show up in amplitude glitches or delay/phase spikes. An example is shown on the Figure K.1.

**Figure K.1:** Example of a XY products with early/normal problem in 6A or 6B.
$\begin{figure} \centering \includegraphics[width=0.5\textwidth]{early_vis2.ps} \end{figure}$

Notice the 8 nanosecond jumps in the delays. Closer inspection using the cross-products on VIS (VISselect ab,cd) is shown on the Figure K.2.

**Figure K.2:** Example of a poor early/normal calibration.
$\begin{figure} \centering \includegraphics[width=0.5\textwidth]{early_vis3.ps} \end{figure}$

Again, the 8 ns jumps are there, but these correlations are based on the noise diode, so that means that you will see the jumps even if you are on a weak source. Comparing the two illustrated plots reveals that there are early/normal jumps before the antennas come on-source, but these only show in the second plot where the delays are not noisy.

Robin Wark 2006-10-24