Untitled Document

SKA SITE SPECTRUM MONITORING IN SOUTH AFRICA
03.05.05

The SKA Site Spectrum Monitoring team consisting of Bou Schipper and Rob Millenaar from ASTRON arrived in South Africa on Saturday 2 April 2005. This signalled the commencement of the SKA site monitoring campaign. This campaign aims to conduct Radio Frequency Inference (RFI) studies at the core site of the respective bidding countries and to enable cross-calibration between the ASTRON standard and locally provided RFI measurements and instrumentation.

Setting up RFI Measuring Systems. The ASTRON mast in the foreground with one of the South African RFI assemblies in the background.

The trip started well with the ASTRON gear arriving safely in South Africa and clearing customs well within the scheduled time frames. The two large shipping crates were unpacked and the individual transit containers loaded onto a trailer for the 1000 km road trip from Johannesburg to the Karoo Farm known as “Losberg” in the Northern Cape.

“Every day in the Karoo is an adventure” says South African SKA RFI team-member Paul Manners. Manners who has been doing most of the RFI measurements at the South African candidate site has had to deal with a number of “adventures”. A few new adventures were on the cards. Assisted by Japie Greef, who’s been responsible for the assembly of the SA RFI measuring systems, the Core site cabin was prepared and the two South African RFI measuring systems set up.

An uncharacteristically overcast day on the 6th of April made the assembly of the ASTRON equipment and masts a pleasant activity. What startled everyone, however, were the thunderstorms and cloudbursts that temporarily turned the farm roads into rivers and over a period of a week the dry semi-desert into a green haven. Considering that the annual rainfall is under 230 mm the cloudburst in the first week of ASTRON’s visit made Rob and Bou very popular with the thankful farmers.

Bou Schipper confirming the outside temperature of 10 °C

Both the ASTRON- and South African SKA RFI Teams were, however, surprised by cool, overcast and wet conditions. “We don’t believe you anymore” is how the ASTRON representatives light-heartedly respond when the South Africans relate accounts of 42°C and heat exhaustion.

With the systems set-up and scheduled measurements about to commence it was time to deal with a few procedural matters. Operation of wide-band radio receiving equipment raises a number of concerns in terms of telecommunications-, broadcast- and interception- and monitoring legislation in South Africa. Representatives of the Independent Communications Authority of South Africa Mr Dave Drew and Danie Lombard welcomed the ASTRON team to South Africa. They advised that the Chairperson and Council of ICASA had agreed to recognise the importance of the ASTRON measurements and in terms of South African broadcast-and telecommunications law had awarded the ASTRON and South African SKA RFI team “Inspector Status”. This formally authorised the RFI survey.

Assisted by the ICASA representatives a set of cross-calibration measurements were conducted. Known reference signals were generated from a calibrated source and comparative measurements taken across the SKA frequency range. Cross-calibration results were recorded via the ASTRON gear and the two RFI systems assembled by the South African SKA team. Joint scheduled RFI measurements commenced on 9 April 2005.

Joint RFI Measurements

A review of the local radio environment highlighted a number of local RFI sources below 300 MHz and a follow-up visit with ICASA representatives was arranged. RFI measurements continued above 1 GHz. The Local RFI culprits including a battery charger, a video display cable and a number of Laptop computers were quickly identified. With the local RFI sources known, characterised and eliminated, measurements below 1 GHz commenced on 21 April 2005.

Life in the Karoo is truly an adventure and the ASTRON team joined right in and added to the list of SKA-adventures: extreme off-road mud driving, replacing flat tyres whilst the sun sets, tracing an urgent courier delivery across the region, meeting the odd unfortunate aardvark on the road at night and dealing with a temperamental computer system.

Gerhard Petrick
Project Manager - RFI
SKA South Africa

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