National Radio Quiet Zone
Description
The National Radio Quiet Zone (NRQZ) was established by the Federal Communications Commission (FCC) in Docket No. 11745 (November 19, 1958) and by the Interdepartment Radio Advisory Committee (IRAC) in Document 3867/2 (March 26, 1958) to minimize possible harmful interference to the National Radio Astronomy Observatory (NRAO) in Green Bank, WV and the radio receiving facilities for the United States Navy in Sugar Grove, WV. The NRQZ is bounded by NAD-83 meridians of longitude at 78d 29m 59.0s W and 80d 29m 59.2s W and latitudes of 37d 30m 0.4s N and 39d 15m 0.4s N, and encloses a land area of approximately 13,000 square miles near the state border between Virginia and West Virginia.
Coordination Requirement
In order to minimize harmful interference to operations in Green Bank and Sugar Grove, all requests for frequency assignments within the NRQZ shall be coordinated by the applicant, prior to authorization, with:
NRQZ Administration Office
National Radio Astronomy Observatory
P. O. Box 2
Green Bank
WV 24944
This procedure applies to all stations except mobile and transportable stations.
Federal Government Transmitters:
All frequency assignments for Federal Government transmitters which are to be located within the NRQZ are required by the National Telecommunications and Information Administration (NTIA) to be successfully coordinated with the NRAO Interference Office prior to the approval of the assignment.
Non-Federal Government Transmitters:
All applicants for non-Federal Government transmitters for certain radio services within the NRQZ are required by the FCC to notify the NRAO Interference Office prior to or simultaneously with the filing of the FCC application. Both a copy of the completed FCC application form and the antenna technical data should be sent to the Interference Office.
Applicants for some radio services are required to file their applications through independent frequency coordinators (e.g. APCO, AASHTO, PCIA, and IMSA). The coordinators assume the responsibility of notifying the Interference Office that an FCC application has been filed and hold the application until the Interference Office responds with its evaluation.
Transmitter Evaluation
The NRAO Interference Office reviews all assignments or applications for new or modified fixed transmitters within the NRQZ to insure that the computed power flux density at the reference point does not exceed frequency-dependent thresholds. In order for the Interference Office to accurately and promptly review the transmitter application, the applicant should forward the following technical data to the Interference Office:
- Name and address of applicant.
- Radio service.
- Frequency of each transmitter.
- Transmitter power.
- Transmission line losses in dB.
- Antenna location(s) in latitude and longitude to nearest second.
- Antenna site ground elevation(s) above mean sea level (AMSL).
- Antenna height(s) above ground level (AGL).
- Antenna gain or horizontal pattern and orientation in azimuth
(in Planet Antenna File Format).
In some instances, the ERPd requested by an applicant exceeds the level that is harmful to observations in Green Bank or Sugar Grove. When this occurs, applicants should discuss possible modifications to their transmitters (e.g. using a directional antenna, relocating the antenna to an area that provides additional terrain shielding, or selecting a different frequency where the power density limits are different) with the Interference Office. In our experience, a technical solution can almost always be found to provide the area coverage desired by the applicant while simultaneously minimizing the impact of the interference upon Green Bank or Sugar Grove. In the extremely rare case when differences between the applicant's desires and the Interference Office's evaluation cannot be resolved, both the applicant and the Interference Office should forward comments on the transmitter installation to the FCC or IRAC for a final resolution.
We emphasize that the Interference Office has no authority in the granting of an FCC license or a Federal Government frequency assignment. The Interference Office only has the privilege of submitting its comments on a particular transmitter installation to the FCC or IRAC.
Applicants who feel that their applications have been evaluated unfairly or inadequately can contact the office of the Green Bank Site Director for a review of their circumstances.
Preliminary Evaluations
As a service to applicants who are planning to install transmitters within the NRQZ, the Interference Office can evaluate proposed transmitter installations long before an applicant decides upon a final transmitter location or equipment configuration. These preliminary evaluations can help the applicant determine the best location for a transmitter while keeping NRQZ interests in mind and can ultimately expedite the application process. The result produced by the preliminary evaluation is the maximum ERPd that can be radiated by the proposed transmitter towards Green Bank. Requests for preliminary evaluations should be submitted to the Interference Office at the above address and should contain the following information:
- Name and address of proposer or future applicant.
- Radio service.
- Frequency of each transmitter.
- Antenna location(s) in latitude and longitude to nearest second.
- Antenna site ground elevation(s) above mean sea level (AMSL).
- Antenna height(s) above ground level (AGL).
Reference Point
The reference point for calculations of transmitter power density is the prime focus of the Green Bank Telescope (GBT). The location of the GBT prime focus is:
Latitude: 38d 25m 59.2s N (NAD83)
Longitude: 79d 50m 23.4s W (NAD83)
Ground Elevation: 806 Meters or 2644 Feet AMSL (NAVD88)
Height: 139.6 Meters or 458 Feet AGL
Power Density Thresholds
Based on a 20 kHz measurement bandwidth, the calculated power density of the transmitter at the reference point should be less than:
- 1 x 10-8 W/m2 for frequencies below 54 MHz
- 1 x 10-12 W/m2 for frequencies from 54 MHz to 108 MHz
- 1 x 10-14 W/m2 for frequencies from 108 MHz to 470 MHz
- 1 x 10-17 W/m2 for frequencies from 470 MHz to 1000 MHz
- freq2 (in GHz) x 10-17 W/m2 for frequencies above 1000 MHz
except for frequencies that reside in the radio astronomy observing bands, in which case the power densities listed in Recommendation ITU-R RA.769-1 shall apply. For a comprehensive list, click here.
Applicable Radio Services
The radio services that are affected by the NRQZ and the FCC rules that discuss them are:
| FCC Rule | Radio Service |
| 1.924 | Public Mobile, Wireless Communications, Maritime, Aviation, Private Land Mobile, Personal Radio, Fixed Microwave |
| 101.105(a)(7) | Fixed Microwave Services |
| 23.20(b) | International Fixed Public |
| 25.203(f) | Satellite Communications |
| 73.1030(a) | Radio Broadcast |
| 74.12, 74.24(i) | Exp., Aux., and Special Broadcast |
| 78.19(c) | Cable Television Relay |
| 97.203(e), 97.205(f) | Amateur Radio (repeaters, beacons) |
NRQZ coordination is also required for the Personal Communications Service (FCC Part 24) and the General Wireless Communications Service (FCC Part 26). These services are not exempt from NRQZ coordination under geographic area licensing.
For more information about the NRQZ please contact:
Phone: 304-456-2107, Fax: 304-456-2276
