Inside installation

Here are some more photographs from the deployment work of the digital beamforming system which was installed on the Kiruna Demonstrator Array.

Putting the final installation into the antenna field. (Photo: D. McKay-Bukowski)

Clock, switch, USRP, receiver... the new approach! (Photo: D. McKay-Bukowski)

Setting up the network and computing. (Photo: D. McKay-Bukowski)

Installing the field equipment

This past week, a team from KAIRA/SGO, LTU and EISCAT have been installing a digital beamforming system on the Kiruna Demonstrator Array. Today, we feature some of the photographs from the installation of the field equipment.

Tomi brings out more USRP subracks. (Photo: D. McKay-Bukowski)

Johan installing the LTU receiver system. (Photo: D. McKay-Bukowski)

Lars-Göran runs the cables back into the main building. (Photo: D. McKay-Bukowski)

Receiver/USRP installation on the Kiruna Demonstrator Array

This week a team from KAIRA/SGO and LTU, together with our colleagues from EISCAT, are working to install a digital beamforming system on the Kiruna Demonstrator Array. During the next week, we'll be featuring a few photographs from this busy time.

The Kiruna Demonstrator Array (Photo: D. McKay-Bukowski)

Current configuration, 6x4 dual-polarisation directional antennas. (Photo: D. McKay-Bukowski)

Lars-Göran digging out the duct entry points. Our previous experience from KAIRA
was absolutely invaluable for this part of the work. (Photo: D. McKay-Bukowski)

Laying the new (bright yellow!) ducting for the network cables. (Photo: D. McKay-Bukowski)

The Kiruna Demonstrator Array

As we wrote earlier, we went to Kiruna last week as part of the planning for the demonstrator array work. The Kiruna EISCAT Demonstrator Array is a phased array of 48 Yagi antennas, arranged in either a 4×12 grid or 4×6 grid... depending on he configuration. It operates at VHF frequencies and is capable of detecting signals from the VHF transmitter in Tromsø.The demonstrator array was mainly built to be an experimental test bed for the digital receivers and digital beam steering that was proposed in the EISCAT_3D design study. Part of the work that the KAIRA team is carrying out is related to this work.

Curious engineers inspect one of the equipment
cabinets. (Photo: D. McKay-Bukowski)

The view along the array. Note the signal cables run
along the frame. (Photo: D. McKay-Bukowski)

Another view (in the sunshine!). But there is still a bit
of snow on the ground. (Photo: D. McKay-Bukowski)

Simple antennas, but lots of them!

Let's resume the story from Monday, when we were discussing the EISCAT Kiruna Demonstrator Array in Sweden. As we saw in that article, the array is a 12 ×4 grid of 48 Yagi aerials. If you look at an individual one of these aerials, you will see it is really very simple. Just a few rods, some bolts and a cable or two. If you look at one before it is assembled, it looks something like this:
Apart from the tools in the lower right of the photograph... that's it!

When built, the aerial looks like this (shown here at the back of the control building at Kiruna in 2006, before the construction of the actual test array). It was simply attached to a post hammered into the ground at roughly the right angle, to look towards a section of the atmosphere being 'illuminated' by the radio signals of the VHF transmitter from Tromsø.


It looks simple.

But that's the whole idea!

In order for EISCAT (or for that matter, KAIRA, LOFAR or SKA) to work, they rely on a multitude of simple antennas. Each one must be capable of receiving the correct radio frequencies with high fidelity, but as cheaply as absolutely possible.

Then, sheer numbers (plus some clever electronics and computing!) will do the rest.

EISCAT-Kiruna Demonstrator Array

KAIRA is not the only project working on the issue of antenna and receiver technology for EISCAT_3D. In addition, there is the so-called 'demonstrator-array', which is located at the EISCAT receiver station at Kiruna, Sweden. I contacted Lars-Göran Vanhainen from the Kiruna site and he explained what this project is all about.

The demonstrator array is a phased array of 48 Yagi antennas, arranged in a 4×12 grid. It operates at VHF frequencies and is capable of detecting signals from the VHF transmitter in Tromsø. The photograph from Lars-Göran shows these Yagi antennas in the foreground. The large dish behind the control building is the 32-metre receiver antenna of the existing EISCAT system.

The demonstrator array was mainly built to be an experimental test bed for the digital receivers and digital beam steering that was proposed in the EISCAT_3D design study. Although the design study has now been concluded, the prototype work is being continued.

The array has now been equipped with fixed delay co-axial beam steering. As it is set up, the array points towards Tromsø at an elevation of 55 degrees, which corresponds to an altitude of 300 km above the Tromsø VHF transmitter. Successful tests have been conducted and bi-static VHF data has been recorded.

Work is now in progress to tilt down the beam to 100 km above Tromsø. The 'beam' is the direction in which a radio receiver array is sensitive. It is a concept like the beam of a search-light, but in reverse; receiving, rather than transmitting.

The objective is to modify the array to be able to do E-region measurements and VHF bi-static studies of meteors and PMSE. These phenomena are both coherent and much stronger than the incoherent scattering from the ambient ionosphere, so even a decrease of the total gain due to the change in the array geometry from optimal should not have an great impact on the measurements in mind.

We'll be talking a lot more about these crucial experiments in future web-log posts!