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