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RFI Management for Single Dish Radio Astronomy at NRAO Green Bank

RFI Management for Single Dish Radio Astronomy at NRAO Green Bank. Some Considerations. Single dish RA is more vulnerable to RFI than array configurations. Protection and source-mitigation are the preferred options but not always possible.

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RFI Management for Single Dish Radio Astronomy at NRAO Green Bank

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  1. RFI Management for Single Dish Radio Astronomy at NRAO Green Bank

  2. Some Considerations • Single dish RA is more vulnerable to RFI than array configurations. • Protection and source-mitigation are the preferred options but not always possible. • Weak, narrowband, or intermittent RFI lends itself to excision; strong, constant, or wideband noise-like RFI does not.

  3. Protection and Mitigation • National/International (Protected Bands) • Regional (NRQZ) • State (WVRAZ) • Site (Site Policy)

  4. NTIA Radio Astronomy Allocated Bands

  5. NTIA Radio Astronomy Allocated Bands

  6. NTIA Radio Astronomy Allocated Bands

  7. NTIA Radio Astronomy Allocated Bands

  8. The National Radio Quiet Zone • Established by an act of congress in 1958 • Approx. 13,000 sq. mile area • Requires coordination for all permanent, fixed, licensed transmitters • Administered through NRAO Green Bank for the mutual benefit of NRAO and the Sugar Grove Facility

  9. WV Radio Astronomy Zone • Established through §37A-1-2 of the West Virginia Code “The Radio Astronomy Zoning Act” • Applies to any electrical equipment that causes harmful interference to Radio Astronomical Observations • Increasingly difficult and complex problem due to the proliferation of wireless technologies • Our Strategy: • Problem-driven component: we will seek enforcement only as a last resort, if friendly requests repeatedly fail. • Proactive component: We solicit voluntary cooperation: PR campaign is in progress to raise awareness

  10. Zones 1 & 2: On-Site RFI Policy • IPG Develops Policy; Site Director has final authority • ITU-R RA.769 Limit applies

  11. Amplifier Assessing Equipment For RFI ComplianceAnechoic Chamber Testing Receive (Rx) Antenna Equipment Under Test (EUT) Cable #1 Cable #2 Distance (Dtest) Spectrum Analyzer Cable #3 PowerTx(dBm) = Pmeasured(dBm) + Lspace(dB) – Gantenna(dB) – Gamplifier(dB) + Lcables(dB)

  12. The “Show Me” Project ~150m

  13. The “Show Me” Project ~3:1 or 5dB SNRatio …but anechoic chamber prediction said worst-case emissions exceed ITU-R line limit by 22dB....17dB discrepancy???? 60s integration time of test vs. ITU-R line limitassumed 2000s integration: 10Log(60/2000) = -15dB (close enough)

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