The Virginia Tech Antenna Group is strategically located on the top floor of Whittemore Hall, a six-story academic building acting as the key administrative and research facility for the university's Bradley Department of Electrical Engineering.  This has given the group easy access to the rooftop antenna testing range since 1985, requiring them to only hike up one flight of stairs.  While this site certainly retains its usefulness today, the need for an indoor testing ground remained pertinent to the group's work.  They desired a place where they could have greater control over the elements that affect the operating characteristics of the antennas they were building and researching.

     Enter the Anechoic Chamber.  The Chamber provides just the environment VTAG needs.  Much the same way a high-fidelity audio recording studio is designed to keep unwanted noise out of the recording, the chamber is built to isolate an antenna and measurement instrumentation from radio frequency "noise" generated by the massive amounts of local consumer electronic equipment, computers, and other RF emitting devices, as well as natural phenomenon.  This isolation is achieved by comprehensive shielding on the outside to reflect external interference and advanced RF energy absorption materials on the inside that reduce confounding results due to internal signal reflection.  The combination creates a near perfect space to more accurately explore the behaviors of different types of antennas without errors created by external sources.

     The decision was made to have the chamber built within the VTAG office suite, specifically in 618 Whittemore.  After some consideration, the group decided to construct their chamber in house as opposed to contracting an outside firm.  Staff engineer Randall Nealy played an instrumental role in the planning and design of the chamber.  He contrived the computer model of what would become the VTAG Anechoic Chamber in a few months' time; a cube, eleven feet in all dimensions, with a nineteen-foot taper section for far-field measurements.  The addition of an equipment access door and some consideration of sensor and antenna positioner equipment provided the final touches, resulting in the final diagram seen below.

     With funding help from the university and the Navy, designs were finalized and construction began on the $500,000 facility. Wall modifications were made to room 618, which to this day doubles as the group's indoor antenna construction lab.  Once space was cleared, groundwork for the chamber started.  The construction materials were simple; pine two-by-fours were used to create the skeletal frame of the structure and the walls were paneled using common plywood.

     Shielding and absorption were the next two concerns the group had when constructing the chamber.  A healthy coating of aluminum was placed on the interior plywood paneled walls of the chamber.  This heavy amount of shielding provides sufficient attenuation of exterior interference sources to further increase the accuracy of the measurements taken.

     Of course, the aluminum reflected inside sources of RF just as good as outside sources of RF, making the chamber like a room of mirrors to the sensors.  The need for some sort of a non-reflective attenuating interior coating was apparent.  NASA catered to the situation and donated to VTAG all the blue "egg-crate-like" RF absorption material.  Sections of this material were cut to fit the geometry of the chamber.  Strips of Velcro were glued to the metal shielding and the backs of the absorber.  This method of application was used to facilitate easy repair of damaged sections, as well as to help preserve the fully-anechoic state of the chamber.

     Once all the structural work was completed installation of the chamber instrumentation.  VTAG turned to Los Angeles-based ANTCOM to help in this area.  ANTCOM custom constructed the chamber's antenna mount superstructure, boasting a seven-axis positioner capable of precisely wielding antennas weighing up to fifty pounds.  They also supplied both the near-field and far-field scanner superstructures, the former also sporting a similar position-varying system.  Agilent Technologies provided the network analysis hardware; the HP8510/8530 and HP8720 are both capable of working with the chamber.  The output of these devices is sent to software developed by Antcom that renders graphical feedback of the data collected in the chamber.