There has been some discussion recently regarding not just polarisation for the HBA, but also cell registration too. As we were already conducting some other tests, we decided to check on this too. In other words, checking the registration of the individual antenna cells within the tile itself.
The cells within the tile are numbered 1-16, starting in the top left and working across. The position offsets of these are set using the iHBADeltas.conf file.
Although we have been reliably using the system, it has not actually been tested directly. To do this, we created a temporary dipole (some wire, a broom and a snow post) and also a screen (kitchen foil between cardboard, taped to an HBA lids' pallet). Using these, we could both transmit into and block signals for a given cell in the tile.
We also made use of some special rspctl commands to disable all the tile elements, except one. This allowed us to check each cell individually.
The only problem in this was getting the snow off the tile.
|A home-made RF block. (Photo: D. McKay-Bukowski)|
Cell #1 is located at the western-most corner of the tile. The cables for the tiles exit underneath cells #14 and #15. Note that this is the not the usual layout for HBA tiles in a LOFAR station. It is just that KAIRA has a slightly different orientation in order to accommodate EISCAT experiments.