Saturday, 28 July 2012

Drawing the line

The LBA-cable-mausoleum (also known as the "Postila mausoleum") is getting pretty full these days. With more and more aerials being installed, it is difficult to manoeuvre in and the cables are getting increasingly hard to pull through. Here are some photographs from this process.

Firstly, it is important to recall that the cables are installed "backwards". Although the signals go from the aerials to the RF-container, the cables are physically installed the other way. Each pair (X and Y polarisation cables for each antenna) are inserted into the ducts and are drawn through the long pipes to the common point at the edge of the LBA field. This is where the LBA-cable-mausoleum is located.

Here, there is a large piece of vertical agricultural drain, large enough to fit a person in, and certainly big enough for a lot of cables. We refer to it as the "U-boat hatch", as that's about the size of it and it occasionally floods with water. (Incidentally, the flooding problem has now been fixed as we've added a new drain to the side to get the water out.) We wrote about the installation of this hatch earlier (LINK).

In the finished state, the cables will go into the mausoleum itself to "burn off" excess length due to the non-uniformity of the array. However, during the installation they are first installed directly into the white ducts that go from the mausoleum to the nodes. There are a number of different cable nodes on the field, each server a few aerials. Each node has its own narrow duct, and the cables need to be fed into the correct duct and drawn through to the node itself.

Feeding the cables in to the white duct pipes. The thin white lines are the draw strings. (Photo: D. McKay-Bukowski)

The cables are pulled through to the nodes where they branch off to the individual aerials according to the trenching plan.

Pulling the cables through to the node. From there, they go in pairs to individual antennas. (Photo: D. McKay-Bukowski)
Once a cable pair has been pulled through into the node, it can be pushed through the remaining duct to the actual aerial location. Once both the aerial end, and the RF-container end, are secured, the excess cable is pulled through to the mausoleum in the centre and is zig-zagged back and forth to tack up the slack.

The cables are then scanned, as we keep an inventory of which cable was installed where. This is important as we need to know the exact lengths and propagation delays used in each location.

Thus, the cable installation for that antenna is completed.

No comments:

Post a Comment