Living with radio interference (rfi) Define Interference Please VDE 0875/71 (Verband der Elektrotechnik Elektronik Informationstechnik) CISPR 22 (Comité International Spécial des Perturbations Radioélectriques) ISO 11451* (International Organization for Standardization) FCC part 15 (Federal Communications Commission) MIL-STD 461 (US military standard) IEC EN 61000-* (International Electrotechnical Commission) EN 55022 (European Norm) Christian Monstein, Institute for Astronomy, ETH Zurich, Switzerland RAS meeting, London 09.05.2014
Radio Astronomy, a Passive Service Among Active Users 1 s integration time, BW ~ 60 KHz, telescope pointing to the sky
RFI and population density Montevideo Uruguay Pop. 1.4 million Bleien, Switzerland Pop. 7 200 Gold mine Castrillon, Minas de Corrales, Uruguay Pop. 3509 (2012)
Radio Frequency Interference Operational conditions of RAS define at what level RFI is damaging detrimental harmful ITU-R RA.769-2 defines detrimental as 10% of system noise power using a reference time interval of 2000 sec and Tsys & bandwidth and 0 dbi entry for each RAS band Such a signal is still buried in the noise of a single observation but will show up after smoothing and in longer integration Define data loss due to RFI as loss of part or all of the band or part or all of the time data loss requires re-observation or total loss in timecritical observations
Defining Radio Quietness ITU Recommendation RA.769-2 Harmful interference levels assuming reception into 0 dbi sidelobe Values for continuum, spectral line and VLBI observations Frequency f (MHz) Assumed bandwidth D f (khz) Input power DP H (dbw) Threshold interference levels Pfd S H D f (db(w/m 2 )) Spectral pfd S H (db(w/(m 2 Hz))) (7) (8) (9) BINGO 151.525 325.3 408.05 611 1 413.5 1 665 2 695 4 995 10 650 15 375 22 355 23 800 2.95 6.6 3.9 6 27 10 10 10 100 50 290 400 199 201 203 202 205 207 207 207 202 202 195 195 194 189 189 185 180 181 177 171 160 156 146 147 259 258 255 253 255 251 247 241 240 233 231 233 (7) Power level at the input of the receiver considered harmful to high sensitivity observations, P H. This is expressed as the interference level which introduces an error of not more than 10% in the measurement of P. (8) pfd in a spectral line channel needed to produce a power level of P H in the receiving system with an isotropic receiving antenna. (9) Spectral pfd needed to produce a power level P H in the receiving system with an isotropic receiving antenna.
Threshold levels ITU-R RA.769-2 Interference threshold levels from Recommendation ITU-R RA.769-2 -160-180 Spectral pfd (db(w/(m2 Hz))) -200-220 -240-260 -280-300 Tx with 1 mw EIRP in 50 khz on the Moon 10 100 1000 10000 100000 Frequency (MHz) Continuum Continuum +15 Line VLBI BAO < 10 nw on the Moon
Radiation limits for electronic devices commercial residential To be on the save side take into account maximum electrical field strength of 50 dbμv/m for any electronic device. Different national and international committees have different opinions about maximum radiation level (CISPR-22, EN55011, FCC part 15, VDE,..) At least FCC defines radiation also above 1 GHz.
Calculations Maximum electric field strength at r = 10 m (FCC) = 50 db [µv/m] = 316.23 µv/m Maximum power flux density P fd = మ = మ ଵଶగஐ = 265.3 pw/m2 Peak power of rfi-source P max = P fd 4π r 2 = 333.3 nw Minimum distance D min in case of free space loss: ௫ ସ ௐ S min according to ITU 100 Jy but much less for BINGO 1 mjy BW = 50 KHz for spectral and 300 MHz for continuum observation Minimum distance D min in case of free space ITU-769: -240 db(w/m 2 /Hz) ~ 100 Jy BINGO: -290 db(w/m 2 /Hz) ~ 1 mjy Spectral BW = 50 KHz 728 km 230 000 km (61% Moon) Continuum BW = 300 MHz 53 km 3 000 km
RFI examples Damage to RAS observations depends on type of experiment Continuum obs. & narrow-band rfi less damaging Continuum obs. & broad-band rfi very damaging spectral line obs. & narrow-band rfi => depends where Spectral line obs. & broad-band rfi => very damaging http://e-callisto.org/generaldocuments/burstcatalog.pdf
How to measure RFI? Automatic dependent surveillance-broadcast (ADS-B) at 1090 MHz Secondary surveillance radar (SSR) at 1130 MHz
Measurement hardware at ETH Zurich
How to deal with RFI? Excision (flagging) or software removal of RFI Additional RFI mitigation possible at RAS station to further reduce manmade signals (in-house and external) Engineering solutions (filters, receivers, coordination distances) All mitigation of RFI in the data leads to Data Loss and lower quality of data Prevention always better than mitigation, e.g. - no webcams within a few km - no electronic environmental sensors close to telescope - no electric motors, no petrol engines using spark plugs, - no electrical fences, no cows with RFI-tags - no mobile phones, no wireless applications - no windmills, no photo-voltaic installations - no electrical devices at all.
How to deal with RFI? Blue: background while windmill is off, red: rfi while windmill is operating
Bleien observatory rfi-map with beam ~4 Day observation 12:36-17:18 excluding satellites
Bleien observatory rfi-map with beam ~4 Day observation 12:36-17:18 including satellites