RF-container

Last week, one of the scientists from SGO was en route to Tromsø and passed by the KAIRA site. Today, we feature a couple of photographs that he took of the RF-container. The first image shows the entire container with the mausoleum in front of it.

The KAIRA RF-container. (Photo: C-F Enell)

It is based on a regular international LOFAR RF-container, but with antennas for communications and, of course, the mausoleum for the delay excesses for the HBA array. Additionally, there is a metal cowling on the western side which protects the air-conditioning unit. This metal shield stops ice and snow from jamming up the air-conditioning unit during winter.

Air-conditioning cowling. (Photo: C-F Enell)

RF-container

Today we just have a nice photograph of the RF-container at the KAIRA site.

The KAIRA RF-container and HBA cable mausoleum. (Photo: D. McKay-Bukowski)

Cable joins

Inside the mausoleum, we found that there had been considerable snow build-up. This may be a contributing factor to the failed join (and that was precisely what it turned out to be). Here are some photographs of the situation as we found it and the problem cable.

Snow of the cables in the mausoleum. (Photo: D. McKay-Bukowski)

The culprit. A loose ground connection, possibly caused by a misseated o-ring. (Photo: D. McKay-Bukowski)

The path to the mausoleum

Despite the service to the aerial, we were still having problems with RCU #84 (Aerial #42, X-polarisation). The next most likely source of the problem would be the cable join. This means opening up tyhe LBA mausoleum (where the excess lengths are located and the joins are placed).

The LBA mausoleum. (Photo: D. McKay-Bukowski)

Getting to the mausoleum is easy. However, opening it up was quite a challenge in the cold conditions.

LBA mausoleum sealed

With winter approaching, and the LBA cabling problem sorted out, we've sealed up the mausoleum ready for winter.

The LBA cable mausoluem, with a bit of frost on the roof. (Photo: D. McKay-Bukowski)

Snow's getting closer

Actually taken a couple of weeks back, but even back then the snowline was descending down the mountain slopes. In the foreground is the RF-container, which houses the KAIRA digital signal processing electronics.

The RF-container at KAIRA, with the HBA mausoleum attached to the front of it. (Photo: D. McKay-Bukowski)

The completed mausolea

The cable mausoleum is used to store excess lengths of the cable from the array. There is one for each of the low-band and high-band arrays. Normally this cable is buried (in what is called a cable 'grave'). However, for KAIRA this needs to be above ground (hence the corresponding term 'mausoleum'). Today we have some photographs by Arttu Jutila of the two completed cable mausolea.

The completed LBA cable mausoleum. (Photo: A. Jutila)

The HBA cable mausoleum, in front of the RF-container. (Photo: A. Jutila)

The LBA cable mausoleum

As you will have seen over the last month or so, the excess cable lengths from the low-band antenna (LBA) array are zig-zagged (not looped!) back and forth in a second mausoleum. Well, this part of the project has now been finished off... and here are some photographs from Arttu Jutila of the work.

All cable work complete and the temporary roof removed ready for the finishing work. (Photo: A. Jutila)

Another view. The frames are converted HBA tile frames, of course. (Photo: A. Jutila)

The next step is to add the purlins. (Photo: A. Jutila)

And then the roof itself is added. (Photo: A. Jutila)

The LBA cable mausoleum

As we've seen recently, we've been adapting cables to get the suitable lengths. However, these lengths are still fixed, and the antennas themselves are are quasi random distances. Thus, there is additional cable to "bury". On conventional LOFAR stations, this is done by physically burying them... hence the term "cable grave". On the KAIRA site, due to the freezing ground and other environmental complications, we have ours encased above ground in a so-called "mausoleum".

Today, as promised, we have some photographs of the fitting of the cables in the LBA mausoleum.

The LBA cable mausoleum. Seen strewn about are some cables that are only partly deployed. To allow us to stop things from getting mixed up and tangled, they are drawn out along the site until they are ready to be inserted into the ducts. (Photo: D. McKay-Bukowski)

The "U-boat hatch". This pipe goes down into the ground to where the entrances to the long main cable ducts are. This is a very cramped space and is quite difficult to work in. (Photo: D. McKay-Bukowski)

Paying out the draw string for the cables. The total duct length is over 50m and pulling the lines through this length can be quite challenging. Even after we opened the intermediate draw pits the force required on the lines is still quite high. (Photo: D. McKay-Bukowski)

Surplus cable in the mausoluem itself. We took immense care to ensure that no looping occurred in the cables as they are folded into the space. (Photo: D. McKay-Bukowski)

LBA cabling

Cabling works had already started for the LBA some time ago, but it is now time to update our readers with the latest situation and photographs.The direction of the cables is from the antennas (yet to be erected) and the RF-container (which is where the signal processing electronics is located). There is a complex tree-pattern of trenching that goes from the antenna field to a common point, where it enters ducts to take the cable underground to the RF-container.

The LBA field during the surveying work. Note the entrance of the cable ducts in the foreground. Photograph by Arttu Jutila.

At this common point, there are various draw lines and a pit where the installation first occurred.

Protective duct at the cable entrance. Photograph by Joona Keskitalo.

This is then back filled to secure this location.

Packing in the soil around the cable entrance. Photograph by Joona Keskitalo.

Finally, there will be another mausoleum placed at this location. The mausoleums are used to take up excess cable length.

Construction starts on the "Markku Postila" cable mausoleum. Photograph by Joona Keskitalo.

This second mausoleum is specifically for the low-band antenna (LBA) array. We have decided to name it after Markku Postila. Markku was the site engineer during the construction of the HBA in 2011. He is also involved in the project again this year, although is spending less time on the site itself.

There will be more photographs as the construction and cabling work progresses.

First light

Electrifying the RF container.

We have first light! Well, not in the conventional astronomical instrument sense no, but we have now managed to get electricity to the RF container, where all of the signal processing will be located.

The cable mausoleum has also got a roof on top of it, which will prevent any snow and ice forming in our cables. Let's hope that the mausoleum will also be rodent-proof once we get the walls on it.

Hooking up to the mains.

Doing the mausoleum roofing work. The owl nesting box can also be seen on top of the RF container.

Cable mausoleum

Another photograph of the work being done on the cable mausoleum. This is the structure where the surplus cable length is zig-zagged back and forth before going into the RF-container.

Here, Pertti Nissinen (left) and Rauno Oikarainen fit the support timbers for the next level of the mausoleum. The white pipes are the ducts that go into the RF-container.

Filling the mausoleum

The cable mausoleum is where the excess cable length is zig-zagged back and forth to use up the extra length between the array and the RF-container. Because of the frozen winter ground it is not possible to directly bury the cables; they must stay free to avoid breakage or stretching. Thus, they are placed on a raised platform (which will be covered later).

Pertti Nissinen and Rauno Oikarainen place some extra cable on the mausoleum table top.

Cable mausoleum

The cable mausoleum is used to store excess lengths of the cable from the array. Normally this cable is buried (in what is called a cable 'grave'). However, for KAIRA this needs to be above ground (hence the corresponding term 'mausoleum').

As will be seen over the next few days, this containment space will end up holding up the surplus signal cable. It is like a table, upon which the excess length will be zig-zagged back and forth. And, at either end, there are ducts going down into some of the few places where cables go underground.

Rauno Oikarainen,Pertti Nissinen and Arttu Jutila assemble the cable mausoleum.

Another view of the mausoleum frame in front of the RF-
container, clearly showing the input and output ducting.

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'.