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RFI measurements at the WSRT
Hans van der Marel
ASTRON
RFI Mitigation workshop, Groningen, 29-31 March 2010
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Introduction
• Astronomical observations– Local or non-local interference
• Spectrum monitoring station• National Frequency allocation table• Test observations for less known bands• Investigations for local interference
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Astronomical observations
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Astronomical observations (2)
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Spectrum monitoring station
• Current station operational since 2005– Latest antenna modification December 2007
• Continuous coverage 20 - 3000 MHz• Scanning 24/7 • Calibrated data• Data in RMDF format• Analysis program available• Data available to CRAF
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Set-up of Monitor Station
R&S HF902 R&S HK309
R&S EB200 receiver
Antenna switch
converter
UTPcoax
coax
coax
coax
Control cable
Control computer To ASTRON network
Roof of construction hall
Construction hall
Main building
Field
Glass fiber
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Rohde & Schwarz EB200 Miniport receiver
• Frequency range 10 kHz - 3 GHz• Noise floor -117 dBm @ 30 kHz BW• Scan speed 126 points/s
20 - 3000 MHz in 13.5 min @ 30 kHz BW
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Rohde & Schwarz antennae
HK 309• Freq range: 20 - 1300 MHz• Passive• Linear polarization
HF 902• Freq range: 1 - 3 GHz• Passive• Linear Polarization (V used)
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Schematic of Control Program
Measurement module
Measurement file
measure.dat
Calibrationfiles*.dat
TCP/IP connection
EB 200 measurement
receiver
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GUI of Control Program
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Header File (*.rmh)
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Schematic of Analysis Program
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Graphical Presentation (1)
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Graphical Presentation (2)
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Graphical Presentation (3)
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Test observations (e.g. 608 MHz)
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Investigations of local or internal interference
• Usually in 1 or few telescopes• Malfunctioning equipment
– E.g. oscillating amplifiers, leaking of LO
• Interfering equipment– Computers, networks, lab equipment
Tools:• Handheld antennas, probes, spectrum
analyzer, receiver• Experience
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Summary
• Astronomical observations are inspected,they are the most sensitive– Autoplots give first indication– Reports from astronomers
• Spectrum monitoring station gives indication about possible RFI
• Test observations can reveal real usability of frequency band
• Good relation with National Agency is important• Know your enemy (e.g. Galileo)• Local and internal interference requires continuous
attention