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October 2010
In this issue
Innovative new design for SA's MeerKAT
New measurements of radio frequency interference at the proposed South African and Australian SKA sites
Africa unites behind continent's SKA bid
IAU Astronomy Development Office will be in South Africa
Global partnerships to meet SKA demands
Developing skills for the future
SKA Africa boosts maths and science at nearby schools
Northern Cape communities gear up to support Africa's SKA bid
HartRAO 26m radio telescope recommissioned
Houwteq Anechoic Room Facility
Updated branding for SKA Africa
New home for SKA Africa in Cape Town

Houwteq Anechoic Room Facility

By Richard Lord, SKA South Africa Project Office, Cape Town

The Houwteq test facilities are operated by the Institute for Satellite and Software Applications (ISSA), a government facility managed by South Africa's Department of Communications. The facilities are located near Grabouw in the Western Cape, about 100 km East of Cape Town.

Today, Houwteq continues to provide excellent facilities for designing and testing small satellites. These facilities include the Metrology Facility, the Integration Facility (which houses the Thermal Vacuum Facility, the Optical Integration Facility and the Optical Calibration Facility) and the Vibration/Acoustic Noise Test Facility. The anechoic room is part of the EMC (Electromagnetic Compatibility) Facility.

Location of the ISSA (Houwteq) facilities and the SKA Africa office in Cape Town (picture Google).

Main entrance to the EMC facility.

The EMC Facility, which is used to subject a device to electromagnetic interference (EMI) and electromagnetic susceptibility (EMS) tests, consists of the following major laboratories:

  • Fully Anechoic Room (FAR) and Associated Control Room
  • Open Area Test Site (OATS) and Associated Control Room
  • Transient Test Laboratory

Fully Anechoic Room.

Open Area Test Site.

The anechoic room facility has an inside volume of 11.5m x 7.5m x 8.5m (height) and provides the capability to do the following measurements to, amongst others, MIL-STD-461E:

  • Radiated emission, electric field: 10kHz to 18GHz
  • Radiated emission, magnetic field: 30Hz to 100kHz
  • Conducted emission: 10kHz to 30MHz
  • Radiated susceptibility, electric field: 10kHz to 18GHz, up to 200V/m CW
  • Radiated susceptibility, magnetic field: 30Hz to 150kHz
  • Conducted susceptibility: 10kHz to 400MHz
  • Electrostatic discharge: 0 - 30kV
  • E-field shielding from environment: >100dB from 1MHz to 18GHz

The OATS measurement facility provides the capability to do the following measurements to, amongst others, CISPR22:

  • Radiated emission, electric field: 30MHz to 2.5GHz
  • Conducted emission: 150kHz to 30MHz

The following specifications apply to the existing OATS facility:

  • Ground plane: 30m x 25m
  • Antenna height: variable from 1m to 4m
  • Polarization change: by compressed air
  • Turntable: 4m diameter, load 4 tonne
  • Test hut: 6m x 4m x 4m composite material

This anechoic room facility was used extensively by SKA Africa to qualify the EMC design and shielding effectiveness of electrical and electronic equipment which forms part of the KAT-7 radio telescope. Self-generated RFI is a major concern for any radio telescope, and the ability to measure and identify RFI in an anechoic chamber forms an important part of the process to keep the telescope site clean. Equipment such as shielded chiller plants, cryostat assemblies, stages of the RF front-end, shielded cabinets inside the antenna pedestals, have all been verified and characterised at the Houwteq anechoic chamber.

Shielded cabinet being tested inside the anechoic chamber.

Cryostat Assembly being measured with horn antenna, set at 1m from the device under test.

Turbo pump test setup with bi-conical wire dipole antenna (horizontal polarization) set at 1m from the turbo pumping station.

Double ridged flared horn in vertical position. Water chiller and CryoTel cooler and controller at 1 m, and power supply at 1.5 m from antenna.

The CryoTel cooler and controller positioned 1m from the horn antenna.

Two SUN servers and a network switch being tested with bi-conical wire dipole antenna.

Although the anechoic room is big enough for a large vehicle to be parked inside, it is not desirable to pollute the radio-absorbent material with exhaust fumes. However, a neighbouring hangar-like building (45m long, 22m wide and 22m high) can, and has been, used instead. The steel reinforced concrete probably provides some amount of shielding from the environment, and comparative tests (between diesel and petrol engines) have been conducted successfully.

Radiated vehicle emissions being measured with log-periodic antenna, and double ridged horn antenna.

The RFI Trailer, with all the RFI measurement equipment inside was recently tested inside the anechoic chamber. The RFI Trailer equipment is being used to conduct further site characterisation measurements, both in South Africa and in Australia. The anechoic chamber has been instrumental in detecting sources of self-emissions, and to verify that subsequent shielding approaches have been successful.

RFI Trailer tested for self-emissions in the anechoic chamber at Houwteq.