RFI Management for Single Dish Radio Astronomy at NRAO Green Bank

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

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Protection and Mitigation

• National/International (Protected Bands)
• Regional (NRQZ)
• State (WVRAZ)
• Site (Site Policy)

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NTIA Radio Astronomy Allocated Bands
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NTIA Radio Astronomy Allocated Bands
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NTIA Radio Astronomy Allocated Bands
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NTIA Radio Astronomy Allocated Bands
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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

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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

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Zones 1 2 On-Site RFI Policy

• IPG Develops Policy Site Director has final
  authority
• ITU-R RA.769 Limit applies

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Assessing Equipment For RFI ComplianceAnechoic
Chamber Testing
Amplifier
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)
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The Show Me Project
150m
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The Show Me Project
31 or 5dB SN Ratio 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 limit
assumed 2000s integration 10Log(60/2000) -15dB
(close enough)