Heavy engineering company Efficient Engineering has delivered 15 radio telescope antennas comprising a stationary pedestal and a rotating yoke, which are being used for the construction of the MeerKAT radio telescope. The MeerKAT will be integrated into the Square Kilometre Array (SKA) Phase I, which is being built near Carnavron, in the Northern Cape.

Efficient Engineering division Efficient Power MD Warwick Jackson tells Engineering News that the next milestone for the company will be the delivery of an additional 17 integrated pedestal and yoke units by the end of April. Final delivery of all 64 units is scheduled for December.

Owing to the complexity of the project and the accuracy required for radio antenna systems, the engineering of the antenna positioners requires significant levels of manufacturing accuracy and repeatability, particularly the slew bearing, which connects the stationary pedestal with the rotating yolk that holds the antenna backup structure.

Local mechanical engineering company Titanus Slew Rings (TSR) is manufacturing the slew rings used on the project. Jackson highlights that TSR has achieved impressive levels of accuracies with its slew bearings and has met the exacting standards of SKA South Africa.

He adds that the integration process of the entire yolk and pedestal assembly, for which Efficient Engineering is responsible, requires the use of an absolute laser tracking system to verify that the slewing system is within the required specifications. This data is then used for the Romer arm to ensure that the installation of the main encoder mount plate is within 50 µmm of all plains relative to the slewing axis. This is all done at Efficient Engineering’s premises prior to dispatch to site.

Another important requirement for the radio antenna is the prevention of unwanted radio frequency interference (RFI) to the highly specialised signal receiver equipment. Jackson notes that there are extremely specialised requirements around the fabrication of the shielded drive compartment to ensure minimal RFI. The shielded drive compartment houses a unique servo system designed by Germany-based satellite antenna specialist Vertex Antennentechnik, which designed the antennas.

he receivers installed by local project developer SKA South Africa on the final antenna assembly are so sensitive to RFI that even relatively low powered transmission signals emitted by commercial electronics, such as mobile phones, could severely damage the receivers.

To further shield the antenna positioner from RFI, Efficient Engineering tests every weld of the outer structure for cracks using dye penetration, as cracks could compromise the RFI shielding integrity of the structure.

Most of the welding is done by a robotic welder with a telescopic boom to achieve the highest level of accuracy and consistency as part of Efficient Engineering’s complete fabrication of both the yoke and the pedestal.

The company is also responsible for manufac-turing a large portion of the other subassemblies used on the antenna. This has assisted in exceeding the stipulation that 75% of the contract value be spent locally.

Before the completed antenna positioner is transported by road to the SKA South Africa site, every aspect of the system is tested for faults by Efficient Engineering, which includes interference testing by independent testing companies and quality assurance. The local prime contractor, Stratosat Datacom, provides unprecendented levels of support for the project. It is this collaborative approach that has seen Efficient Engineering’s scope of work for the project continue to grow.

This approach and the company’s close relationship with Stratosat Datacom make for a healthy working environment and prevent unnecessary on-site delays, as the fully integrated yoke and pedestal assemblies require only simple installation on site. Once delivered to site, the yoke and pedestal assemblies are erected and commissioned within 24 hrs, after which the elevation assembly, is lifted onto the pedestal.

Jackson asserts that the Meer-KAT project demonstrates that South African companies can handle global projects and deliver high-quality engineered solutions.