Tuesday 11 March 2014

LBA aerial problems

Along similar lines to yesterday's web log report, we've also carried out tests for all the aerials of the Low-Band Array (LBA). Here, we also have problems, although the situation is more complicated. Like yesterday, we shall start with a plot of all subbands for all RCUs configured for the LBA aerials.

As can be seen, there are a number which show abnormalities. Most of these are suppressed signals, sometimes causing a shift in the peak amplifier response frequency. This is likely to be caused by snow, as seen in one of our previous reports.

However, the effect on RCUs 68 and 69 is more serious. This looks like a destroyed aerial.

If we plot these onto a map of the array, the positions of the affected aerials are as follows:

One thing to note is that the signal processing chains can be cleared of any faults. The problem with the HBA was on RCUs 80 and 81, but this was absolutely fine for the LBA. The same applies the other way; for example, RCUs 68 and 69 are down here, but were okay on the HBA.

What needs to be done now is to evaluate the situation, especially with aerial #34.

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