Galfa pixel 4a/6a switched may05


    The cables for pixel4a and pixel6a (count from 0)  from the distribution amplifiers in the receiver room to the galfa spectrometer were switched sometime in early may05 (or late apr05). This meant that when  looking at the data offline:

This occurred when the distribution amplifier chassis for polA was removed to install some fans for cooling. When the chassis was reinstalled, the cables leaving the chassis were switched.

    Continuum sources drift/move through the alfa beams at different times since the beams point at different locations in the sky.  600 second total power scans showed that pixel 6a and pixel 4b had continuum sources moving through the beams at the same time (6b and 4a also showed this). The last "good" data set that showed know cable switch was 12dec05. The next data set available after this was 02may05. The second data set showed the cables being switched (i didn't find any data between these two dates to test).
    The plots show the total power drifts versus time after and before the switch (.ps) (.pdf). Each pixel is plotted in a different color. For each color there are two strips: polA and then polB over plotted:

When inspecting the cables that left the back of the polA rack in the receiver room, we found that it was the polA cables that were switched. This problem only affected the galfa spectrometer. The wapp data was never switched.


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