Caption : Completed signal cables, all neatly plugged into the RCUs (Receiver Units) within the RF-container.
Friday, September 3, 2010
Analogue input cabling complete
By now the patching of all the analogue cables was complete. This represents another major part of the installation work and it was very gratifying to see all the F-type connectors done up and cables bundled.
Caption : Completed signal cables, all neatly plugged into the RCUs (Receiver Units) within the RF-container.
Caption : Completed signal cables, all neatly plugged into the RCUs (Receiver Units) within the RF-container.
Thursday, September 2, 2010
Digital signal processing
While the HBA tiles are being completed, work continues on the installation of the digital signal processing electronics.
Caption 1 : After the signal has been digitised, there are a number of tasks that are done on the data. Firstly, there is the initial delay compensation which is applied for the lengths of the cables. Because the cables across the fields are different lengths, due to the physical distances, this needs to be corrected. Then the received signal is divided into sub-bands, a bit like radio channels. A small sub-set of these are selected and are then combined to final beam, thus selecting the part of the sky to be observed.
Caption 2 : Additionally, statistics are calculated and engineering parameters are monitored. These are used to not only analyse the data for interesting features or to apply calibration corrections, but also to ensure that the equipment is performing correctly and to detect potential errors or interference.
Caption 1 : After the signal has been digitised, there are a number of tasks that are done on the data. Firstly, there is the initial delay compensation which is applied for the lengths of the cables. Because the cables across the fields are different lengths, due to the physical distances, this needs to be corrected. Then the received signal is divided into sub-bands, a bit like radio channels. A small sub-set of these are selected and are then combined to final beam, thus selecting the part of the sky to be observed.
Caption 2 : Additionally, statistics are calculated and engineering parameters are monitored. These are used to not only analyse the data for interesting features or to apply calibration corrections, but also to ensure that the equipment is performing correctly and to detect potential errors or interference.
Completing the last tile.
Mid-afternoon on Thursday 14th July 2010, the installation of the 97 HBA
tiles at LOFAR Chilbolton was completed. Once again, we take the
opportunity to thank everyone who was involved in this part of the
project. The completion was reported at the time (Ref:
http://blog.lofar-uk.org/2010/07/all-97-hba-tiles-installed-in.html),
but here are the photographs of the final stages of the last tile. It is
hard to believe that less than four months before, it was still and
empty field.
Caption 1 : Zabet Ahmadi (left) and Richard Whittaker apply the cover
and start fixing the anchor connections.
Caption 2 : Here's a close-up of that strange object in the wheelbarrow
at the bottom right of the previous photograph. It is the working plan
of the HBA installation, showing the serial numbers, positions and
sequences of the tiles as they were put in.
Caption 3 : With a smile of relief, Zabet Ahmadi connects the final
anchor on the last tile.
Caption 4 : All done!
tiles at LOFAR Chilbolton was completed. Once again, we take the
opportunity to thank everyone who was involved in this part of the
project. The completion was reported at the time (Ref:
http://blog.lofar-uk.org/2010/07/all-97-hba-tiles-installed-in.html),
but here are the photographs of the final stages of the last tile. It is
hard to believe that less than four months before, it was still and
empty field.
Caption 1 : Zabet Ahmadi (left) and Richard Whittaker apply the cover
and start fixing the anchor connections.
Caption 2 : Here's a close-up of that strange object in the wheelbarrow
at the bottom right of the previous photograph. It is the working plan
of the HBA installation, showing the serial numbers, positions and
sequences of the tiles as they were put in.
Caption 3 : With a smile of relief, Zabet Ahmadi connects the final
anchor on the last tile.
Caption 4 : All done!
Lifting the final tile
On Thursday the 14th July, the final HBA tile was prepared and lifted into place.
Caption 1 : Held aloft by the 18-tonne digger, the crew carefully move the final tile across from the unfolding station to its place in the corner of the HBA field.
Caption 2 : Preparing for landing. Here the crew guide the tile into place as it was lowered down. This was actually more difficult than it may at first appear, as there was a stiff breeze making the handling of the tile difficult.
Caption 1 : Held aloft by the 18-tonne digger, the crew carefully move the final tile across from the unfolding station to its place in the corner of the HBA field.
Caption 2 : Preparing for landing. Here the crew guide the tile into place as it was lowered down. This was actually more difficult than it may at first appear, as there was a stiff breeze making the handling of the tile difficult.
Wednesday, September 1, 2010
Last of the analogue signal path
With the sub-rack assemblies now in place, the signal cables can be connected. These come from the patch panels, under the false floor and up onto the F-type connectors on the front of the processing units. Until now, the signals have been analogue from the antennas, front-end amplifiers and electronics through to this point. Once they go into the receiver units they are subjected to some final amplification, switching and filtering, but are then digitised. From then on, the signals are digital and all subsequent processing happens in the digital domain.
Caption 1 : The first batch of cables are fed under the racks and are connected onto the front of the RCUs (Receiver Units)
Caption 2 : Sientje Hartman (Excel Assemblies) makes excellent progress in patching the signal cables into the RCUs. Soon many of the panels are covered in connections.
Caption 1 : The first batch of cables are fed under the racks and are connected onto the front of the RCUs (Receiver Units)
Caption 2 : Sientje Hartman (Excel Assemblies) makes excellent progress in patching the signal cables into the RCUs. Soon many of the panels are covered in connections.
Sub-racks ready for cabling
Within the LOFAR RF-cabin, there are four, full-height 482.6mm (19") rack frames. The sub-rack assemblies go into the first three of these and the fourth is for the control computers, clocks and networking. Once the sub-rack assemblies are in place, they can be cabled up with the white signal cables that come from the back of the patch panels.
Caption 1 : Tonjes Jipping and Peter Gruppen lift the last sub-rack assembly into the RF-container and secure it into its rack frame.
Caption 2 : Ready for cabling! The signal processing electronics are now in place and are ready to be connected up.
Caption 1 : Tonjes Jipping and Peter Gruppen lift the last sub-rack assembly into the RF-container and secure it into its rack frame.
Caption 2 : Ready for cabling! The signal processing electronics are now in place and are ready to be connected up.
The other side of the cable patch panels
For those of you who were following the work on the cables during the early days of the LOFAR-Chilbolton installation, you may recall that they went from the aerials and tiles, through the trenches under the ground before eventually surfacing at the RF-container. There, they were patched in to the outside of the RF shielding on a special patch panel (Ref: http://blog.lofar-uk.org/2010/05/all-patched-in.html). On 13th July 2010, the installation picks up where that work left off... on the other side of the patch panels.
Caption 1 : Ineke Mol (from Excel Assemblies) starts patching in cables for the LBA.
Caption 2 : The LBA cables are now complete. From the inside of the patch panel, the LBA cables snake their way under the false floor over to where they enter the signal processing sub-racks.
Caption 3 : Here, you can see some of the LBA cables that are now ready. They are the ones that lead off the top of the photograph. The coiled cables have not yet been fully deployed and are waiting for their installation.
Caption 1 : Ineke Mol (from Excel Assemblies) starts patching in cables for the LBA.
Caption 2 : The LBA cables are now complete. From the inside of the patch panel, the LBA cables snake their way under the false floor over to where they enter the signal processing sub-racks.
Caption 3 : Here, you can see some of the LBA cables that are now ready. They are the ones that lead off the top of the photograph. The coiled cables have not yet been fully deployed and are waiting for their installation.
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