Wednesday 27 July 2011

HBA cable lengths

Because it is important to control the cable lengths for the phased array, each cable is made to a specific length. And to ease the manufacturing process, these lengths are standardised to a small number of set lengths. These are divided across the array as follows:

For the KAIRA HBA, there are two set lengths: 85 metres (blue) and 115 metres (amber). The grey/white tiles in the diagram are the positions of a full international HBA. These are not being implemented now, but are reserved as possible future locations.

The total number of cables is 96. That is because there are two cables per tile. The numbers on each tile are their ID numbers (e.g. H74); beneath is the actual distance required (e.g. 109.5m).

Because of the positions of the HBA tiles and the set length cables, there can be several tens of metres of excess cable which needs to be carefully zigzagged back and forth before the remainder of the cable goes into the RF-container. These will be stored above ground.

As on a normal LOFAR international station, the buried cables are referred to as being in a 'cable grave', the KAIRA above-ground surplus storage unit is referred to as the 'cable mausoleum'.

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