1. RFI2010, March 29-31 2010 Groningen R. Ambrosini et al. 1 Roberto Ambrosini IRA-INAF ambrosini@ira.inaf.it “Old” hints to mitigators from the latest RFI experiences Claudio Bortolotti, Mauro Roma, IRA - INAF Pietro Bolli, F. Messina, F. Gaudimonte OAC – INAF

2. RFI2010, March 29-31 2010 Groningen R. Ambrosini et al. 2 Content: From Analog to Digital modulationFrom Analog to Digital modulation Regulatory aspects in Italy about the installation an Eolic park close to SRT (Sardinia Radio Telescope: 64m dish, 100GHz).Regulatory aspects in Italy about the installation an Eolic park close to SRT (Sardinia Radio Telescope: 64m dish, 100GHz). Some operational considerations

3. RFI2010, March 29-31 2010 Groningen R. Ambrosini et al. 3 Tricks to fill the “60dB gap” RA-769 levels are reachable only within radio astronomical observations.RA-769 levels are reachable only within radio astronomical observations. Typical monitoring surveys are less sensitive (-60 dB typ). To fill the gap in S/N, it is common to use in front of a spectrum analyzer: high gain antennas; low noise preamplifiers (filtered); a mobile van, to reduce the distance from the interferer source or getting it within line of sight, shrink the bandwidth around the Analog carriers

4. RFI2010, March 29-31 2010 Groningen R. Ambrosini et al. 4 How the digital spectrum appears now (1) No more narrowband carriers…….No more narrowband carriers……. –reduced sensitivity detection: S/N does not depend on measuring Bandwidth; average levels are intrinsically lower (/channel); spectra are very similar to the radioastronomical observable; Consequences:Consequences: monitoring –On monitoring : more difficult to reach ITU-769 levels; antenna gain vs coverage tradeoff

5. RFI2010, March 29-31 2010 Groningen R. Ambrosini et al. 5 How the digital spectrum appears now (2) harder to discriminate among different interferers; transientlarger incidence of transient interferers (es. city buses, mobile wifi, etc) no simple identification of the interferer (coded ID) –On receiver design: peak voltage and total powerthe Rx dynamic range has to match the peak voltage and total power applied to the active junctions; we expect higher out of band emissions (see the TV case)

6. RFI2010, March 29-31 2010 Groningen R. Ambrosini et al. 6 The TV case

7. RFI2010, March 29-31 2010 Groningen R. Ambrosini et al. 7 Analog TV -60dB

8. RFI2010, March 29-31 2010 Groningen R. Ambrosini et al. 8 Digital TV -60dB

9. RFI2010, March 29-31 2010 Groningen R. Ambrosini et al. 9 The SRT status

10. RFI2010, March 29-31 2010 Groningen R. Ambrosini et al. 10 Regulatory premium Even if narrowband, allocated bands (and in particular the exclusive ones under 5.340) allow: –accurate calibrations of RA observations –reference benchmarks for the experimental verification of mitigation techniques –we can use them as a real deterrent against interferers (like wind turbines)

11. RFI2010, March 29-31 2010 Groningen R. Ambrosini et al. 11 The wind turbine case for SRT The Italian Administration is our legal referee in a confrontation case with any interferer, so we have first asked their assistance in all future contacts with the counterparts. Art. 97 of the Unique Text of the General Code for Communication says: –1 - “Whoever makes activities that, in any way, produce a damage to a communication service, is punishable under the Penal Code……. –2 – “Assured the above, it is prohibited to jam or produce interferences to a communication service….

12. RFI2010, March 29-31 2010 Groningen R. Ambrosini et al. 12 Some operational considerations We have recently defined a feedback form to be filled by the Observing Scientist We ask for specific RFI events and Data Loss (justifying for example some extra observing time) Finally….. please consider: Common Human Brain Speed vs Wireless Bandwidth….