HBA tile #75 flat-lining

Following the high winds of 08-Mar-2013, we carried out a series of remote system tests to verify that KAIRA is still okay and functioning correctly. The best way to do this is to examine the spectrum of every antenna for each polarisation. These are processed by the Receiver Units (RCUs) and there is one for each antenna/polarisation.

The first test we did was for the High-Band Array (HBA). The following is the collected set of spectra for the entire HBA. We expect a broad "Saana-shape" spectrum with occasional vertical spikes of radio-frequency interference (RFI).

As can be seen, there are a couple of weak channels which show non-typical spectra. The RCUs are 80 and 81, which correspond to tile #75 X-polarisation and Y-polarisation. This indicates that there is a problem with the entire tile, and further investigation is needed. Here is the location of the tile in the array:

Given that this is the leading edge against the northwest gales that we have had makes us very nervous.

An expedition to the site will be required.