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FAA upgrades analog microwave network for traffic control centers.

The Federal Aviation Administration is in the final inspection and cut-over phase, leading to acceptance of an 8 GHz analog microwave network with AT&T as the primary contractor.

Known as Radio Communications Link (RCL), the network interconnects Air Route Traffic Control Centers (Centers) located in major cities throughout the U.S.

The Center is the FAA's largest facility. Its primary function is to monitor and control aircraft passing through its designated airspace. The equipment rooms are located in the basement with the air traffic control room overhead.

There are special-purpose rooms for radar, communications, computers, and telco. The Center has as much wiring as a typical telco central exchange. None of the Centers is located at an airport.

The RCL system connecting these Centers replaces the aging (vacuum tubes) Radar Microwave Link (RML) network. As the acronym implies, the RML system's was used to link the Centers to remotely located, long-range radar installations. This is true for the RCL as well.

Images generated at radar sites are routed over the rCL to the Center, where they are repeated on screens at air traffic controller positions.

The image on the CRT at the radar site is converted to digital format through the CD (common digitizer). Paradyne modems are used to send and receive data to the Center. Full duplex operation is required to accommodate radar control signals originating at the Center.

The RCL transmission system is the AT&T 960-channel, frequency diversity, 8 GHz FR-8 radio. Karkar multiplexers to accommodate three supergroups have been installed at each Center. DSC Communications has tentatively been selected to supply muxes for the remaining supergroups.

System alarms are monitored at the Centers through the ACORN telemetry system. Dishes and wave-guide were supplied and installed by Gabriel Electronics of Maine. Drop and insert capability is accomplished with DSC Communications (Granger) DTL 7300 channel modems.

The RCL also is used to tie the Center to other facilities in the air traffic system.

For instance, the RCL might link the Center to an Air Traffic Control Tower, a Flight Service Station, or a Remote Communications Facility housing ground-to-air radios.

Because air-to-ground transceivers have a limited range, 75 to 100 miles, methods for accessing these Remote Communications Facilities from long distances have been developed. By linking the Center to the remote facility through the RCL, a controller can communicate with aircraft hundreds of miles away.

In an effort to reduce the agency's reliance on leased telco lines and provide greater flexibility, the FAA intends to tie as many of its facilities as feasible to the RCL network.

While details on the national Low density RCL Program are sketchy, engineers based at the FAA Southwest region headquarters in Ft. Wroth, Texas, have initiated several such projects.

At Albuquerque, New Mexico, for example, a newly constructed Automated Flight Service Station has been linked to the RCL backbone. Using Western Multiplex baseband bridging equipment and one-2000 2-GHz analog radios, the Albuquerque AFSS was tied to the RCL and became operational last spring.

This link enables the AFSS to access Remote Communications Facilities (RCF) located in southern New Mexico and Arizona. In addition, this link in conjunction with BIA 2 GHz links, completes a loop between Washington Pass and Radar and Albuquerque Center, providing alternate routing.

At Farmington, New Mexico, an RCF associated with Denver Center is being tied to the RCL backbone to add a diversity in additional telco circuits.

Future networking projects in New Mexico will center around an Air Traffic Control Tower to be built at Albuquerque's airport.
COPYRIGHT 1991 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1991 Gale, Cengage Learning. All rights reserved.

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Title Annotation:Federal Aviation Administration
Author:Swartout, Doug
Publication:Communications News
Date:Sep 1, 1991
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