1. RFI measurements at the WSRT Hans van der Marel ASTRON RFI Mitigation workshop, Groningen, 29-31 March 2010

2. 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

3. Astronomical observations

4. Astronomical observations (2)

5. 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

6. Set-up of Monitor Station R&S HF902R&S HK309 R&S EB200 receiver Antenna switch converter UTPcoax Control cable Control computer To ASTRON network Roof of construction hall Construction hall Main building Field Glass fiber

7. 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

8. 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)

9. Schematic of Control Program Measurement module Measurement file measure.dat Calibration files *.dat TCP/IP connection EB 200 measurement receiver

10. GUI of Control Program

11. Header File (*.rmh)

12. Schematic of Analysis Program

13. Graphical Presentation (1)

14. Graphical Presentation (2)

15. Graphical Presentation (3)

16. Test observations (e.g. 608 MHz)

17. 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

18. 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