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. 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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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.

  • Weak, narrowband, or intermittent RFI lends itself to excision; strong, constant, or wideband noise-like RFI does not.


Protection and Mitigation

  • National/International (Protected Bands)

  • Regional (NRQZ)

  • State (WVRAZ)

  • Site (Site Policy)


NTIA Radio Astronomy Allocated Bands


NTIA Radio Astronomy Allocated Bands


NTIA Radio Astronomy Allocated Bands


NTIA Radio Astronomy Allocated Bands


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


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


Zones 1 & 2: On-Site RFI Policy

  • IPG Develops Policy; Site Director has final authority

  • ITU-R RA.769 Limit applies


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)


The “Show Me” Project

~150m


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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