National Radio Dynamic Zone (NRDZ)

This NSF-funded effort supports (1) the development of an NRDZ concept definition, (2) design and development of prototype advanced spectrum monitor (ASM) devices, and (3) broader impact efforts related to spectrum awareness and spectrum management. This article (2018) appears to be the origin of the idea of an NRDZ.

NRDZ Concept Definition:

When we consider precisely what an NRDZ might be, we need to carefully explore how it would potentially be used by various stakeholder communities. While communities and subcommunities have differing use cases, the unifying motivator for all stakeholders that has come through clearly in discussions is increased spectrum access. That is, passive users (radio astronomy and remote sensing) are developing receivers with ever wider bandwidths to increase sensitivity (and reduce observing time), and active users are developing transmitters and receivers that require broader bandwidth for faster throughput of information for an increasing number of wireless-enabled systems.

There are two fundamentally different NRDZ models that have been discussed, referred to in some stakeholder discussions as (1) a “Coordination Zone” (with various levels of management and enforcement), versus (2) a “Wild West” (with little to no enforcement). Both have advantages and disadvantages, but to be clear, some sort of coordination, management and monitoring will be required in either model. In general, the first model is more appealing to the radio astronomy and remote sensing communities, as careful coordination (manual or automated) will be required for sensitive receivers to function in the coming decades. The second model is more appealing to the active community because it would allow a large amount of freedom in the testing of new equipment, and the testing of new theoretical models of propagation.

For all stakeholders, an NRDZ could provide an established location to perform both individual and coordinated experiments that allow them to utilize broader bandwidth. Controlled experiments performed in an NRDZ may have wider applicability if proven there. There have been a number of workshops that explore the idea of an NRDZ. The NRDZ partnership website contains a summary of discussions that took place during 2021-2023. NRAO has been a partner in organizing and leading these discussions, and the Green Bank Observatory will host an NRDZ conference in September 2024.

In order for an NRDZ to succeed, all potential users must be able to point to tangible benefits to their community. In stakeholder discussions thus far, this appears to be possible. In an NRDZ, active users would gain managed access to spectrum currently not available. Passive users would gain access to broad bandwidth observing without the need to undertake complex RFI monitoring and mitigation, and potentially the opportunity to test automated coordination systems with next generation wireless transmitters.

Broader Impacts:

The NRDZ Broader Impacts curriculum includes a citizen science project, a high school curriculum, and an undergraduate curriculum, all focused on increasing the number of students and citizens aware of the spectrum as a finite resource for both science and commerce. These curricula are now complete, and have been made available via the Superknova website. New funding from the NSF is enabling NRAO to work on several new projects in 2024, including the development of an RFI demonstration for science museums and an RFI Citizen Science project.

Advanced Spectrum Monitor (ASM):

One of the NRDZ deliverables is to design, develop and oversee the installation of an ASM prototype. The initial "proof of concept" device was tested in May 2023 at both the Central Development Laboratory (CDL) in Charlottesville and the Green Bank Observatory (GBO). Lessons learned from the testing of this device have been folded into the successor device, dubbed ASM-2.

The "Proof of concept" ASM-1 device deployed for testing at the GBO in May 2023.

ASM-1 (Proof of Concept Device) during on site RFI (anechoic chamber, above) and field testing at the Green Bank Observatory (below) in May 2023.

The first "proof of concept" device was capable of receiving, determining vectors to, and categorizing signals from frequencies of 1 to 20 GHz. Hemispherical coverage is required as potential interferers can be terrestrial or space borne. Frequency, Signal strength, Polarization and Spectral Occupancy was measured and logged by the device. 

Sample spectra from 1-5 GHz taken with the ASM-1 device at CDL (orange) and GBO (blue). While the RFI environment is clearly better at the GBO, the National Radio Quiet Zone (NRQZ) is not completely quiet. Signals near 2.4 GHz are from WIFI networks.

The ASM-1 and ASM-2 are both designed in the form of a pyramid with multiple antennas built into the perimeter of the outer shell. This configuration has allowed for the device to determine azimuth and elevation of emitters. Each antenna is sampled individually, allowing for the amplitude measurements to be entered into an algorithm that will determine a two-dimensional vector (azimuth, elevation) to the radiating source.

The ASM-2, currently being tested and assembled at the CDL will expand frequency coverage from 1-50 GHz, covering the same range of frequencies observed by the JVLA in New Mexico.

Current (January 2024) mechanical drawing of the ASM-2 enclosure. Access to the faces is enabled by hinged doors. Device will be able to be secured and operated in an outdoor environment. 

Update (August 2024): ASM-2 development continues with the construction of the first redesigned sinuous antenna (below) that will be sensitive to the lower portion of the of the spectrum (1-20 GHz). The full device will cover 1-50 GHz. One of these antennas will be on each face of the new ASM-2, giving direction finding capability to the spectrum monitoring device.

The first redesigned ASM-2 Sinuous Antenna on the bench at the Central Development Lab (CDL) in Charlottesville, VA.

NRDZ LOGOS

These logos are freely available for use by any NRDZ-related projects. If there are different formats needed, please reach out to the NRDZ Project Director, Chris De Pree.