Ground Planes

ith the ground work reaching its final stages, it is time to start thinking about the installation of the aerials. This means organising the various components and moving them into place ready for deployment.

In the picture Dave King (left) and Mike Willis set down a stack of LBA ground planes.

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All patched in

As the LBA cables were going into place, the patch panel within the RF container was slowly filling up. After what seemed an eternity, the last cable was drawn through and patched into the cabinet and the panels were complete.


Dave King prepares to insert the last cable into the patch panel and then complete the cable-dressing.


Looking down from the HBA panel, into the duct from whence the cables arrived from the antenna field. Look at how little of the 200mm duct was used in the end... how's that for neat? In fact, there's an open challenge to any other LOFAR station to do better!



All done. The HBA (top) and LBA (bottom) patch panels, fully populated and ready for the next phase of the LOFAR construction process.

Sand People

Now that the HBA cables are in place and patched into the RF-container, the HBA cable grave can be filled in.

First a thick layer of protective sand is spread across the cables. The crew work the cables gently to ensure that the sand penetrates between all of them.


Here is the finished sand cover. This protects the cables against flint and other sharp rock as the spoil is back filled into the grave.


With all cables completely covered, the digger moves in to bulk fill with previously excavated material. And that is it! The HBA cables are fully covered and the crew can walk through the area without the risk of falling into the hole or collapsing a trench wall.


There have been many people involved in the laying of the HBA cables, and here are a just a few of them. From left to right: Dave King, Jon Eastment, Mike Willis, Alejo Martinez-Sansigre and Harry Smith. To these few, and everyone else involved in this stage of the project: thanks and well done!

Home stretch for the HBA cables

After what seems like years to them, the folks at Chilbolton are now reaching the final stages of the HBA cable installation. However, everyone is acutely aware that the LBA (with its labyrinthine trench network) awaits us and time is pressing.

Dave King gathers the strands within the cable grave. This extra-wide trench is used to take up the slack from the fixed length cables.


Richard Armstrong gazes down into the abyss... well, maybe just the last trench where the entry points to the RF-container ducting are. From here, pairs of cables are gathered and passed down for feeding into the ducts.


Well, if Richard was gazing into the abyss, then Chris Caddell is in it! Here, Chris sends the cables through the ducts to the patch panels for final termination.


With the cables patched, it is then time to clear the trenches and gather the cables prior to covering with sand and backfilling. In particular, the trench must be free of any flint which can easily cut into the cable. This is not easy, especially in the final trench where all the cables are present and crowd one another. As this photo shows, the cable crew are obsessed about achieving a perfect job. From left to right: Jack Hickish, Chris Caddell and Kahinde Johnson.

Disentanglement

One of the consequences of various tasks being ahead or behind the schedule is that the folks at Chilbolton have been forced to deploy all the HBA cables before the RF-Container was ready to accept them. This has been good in that they have been able to get the cables laid into the trenches without incurring further delays. On the other hand, they now need to sort out these cables to feed them in the correct order into the RF-container. Quite a task as you will see!

A bundle of cables... thankfully all electronically labelled. A barcode reader and some home-built software will quickly identify the antenna position associated with each cable.


Stuart Lynn, (our "All in the Gutter" live tweeter) Izabela Bukowska and Cristina Fernandes trace a cable in preparation for its deployment into the final trench to the RF-container.


The first cable pair reach the patch panel (Y & X polarisations for HBA antenna #95).


Alejo Martinez-Sansigre, Dave King and Mike Willis continue work on patching cables into the RF-container


Some more of the day's cable-team (left-to-right): Roger Deane, Cristina Fernandes, Alejo Martinez-Sansigre and Stuart Lynn.

Power to the... RF-container!

Work continues on the RF-container. One major step was accomplished today, with the application of power. This event marks the culmination of weeks of trenching, cabling and installation work. The test certificates are now all in place and this afternoon, the final checks were performed before power was applied.

In this first picture, Dave King performs the final inspection of the switch boxes prior to activation.



And here, with the final switch, Dave King activates the final circuit and the RF-Container is energised! They now have mains power on the LOFAR Chilbolton site.

HBA Cable Graves

In the foreground of this photograph you can see the so-called "cable grave" for the High Band Array (HBA). Because it is important to control the cable lengths for the LOFAR radio telescope, 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. Because of the positions of the HBA tiles, 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.

In the photograph, Harry Smith and Dave King are adding another cable to the cable grave. In the background, the ground works crew are adding a layer of sand to protect the recently laid cable.

Pre-Installation Cable Testing

An international LOFAR station is made up of two fields of 96 antenna elements each (96 LBAs and 96 HBAs). Given that each antenna can receive in two polarisations which both need their own cable, this makes for a total of 384 cables between the antennas themselves and the RF-container. Together, these cables have a combined length of 36,360 metres (just over 22.5 miles).

The cables will be buried into the ground before the antennas are deployed. However, before doing this, each one needs to be tested for its electrical characteristics. It is painstaking work, but this verification work is extremely important.




In the picture, Mike Willis and Harry Smith are very happy to have completed the last of the lab testing of the 384 cables.