RFI measurements at the WSRT
Hans van der Marel
ASTRON
RFI Mitigation workshop, Groningen, 29-31 March 2010
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
Astronomical observations
Astronomical observations (2)
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
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
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
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)
Schematic of Control Program
Measurement module
Measurement file
measure.dat
Calibrationfiles*.dat
TCP/IP connection
EB 200 measurement
receiver
GUI of Control Program
Header File (*.rmh)
Schematic of Analysis Program
Graphical Presentation (1)
Graphical Presentation (2)
Graphical Presentation (3)
Test observations (e.g. 608 MHz)
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
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
Top Related