August 5, 2004 (by Dennis Bessire) - The Nose Radome Electrical Test System - which has been operating at Hill AFB using 25-year old technology - is receiving a well-deserved upgrade. The system tests disturbances and variations in the sending and receiving of microwave radar signals through the nose of the F-16 Fighting Falcon.
Bobby Luna, lead systems engineer for Microwave Instrumentation Technologies, and Allen Lawrence, electronics engineer for the Air Force, have been working on the system for 2 1/2 years.
"We're working with the equipment that serves as both a protective covering and a lens for the radar targeting equipment," Mr. Lawrence said.
The problem with the radar dome, also called a radome, can be put very simply: it gets in the way. The nose of the F-16 holds far more than meets the eye - it is responsible for housing and protecting the fire and control antenna, while also serving as a lens for the microwaves to pass through.
The antenna inside sends out a signal, and then receives a reflection signal from anything that might be in the air or on the ground. A radome will deflect, reflect and absorb some of the strength of a signal. This can result in a pilot being incapable of determining exactly where a potential target is, or potentially render the pilot unaware of the presence of a target or threat. It's even possible for the radome to cause false reflections, meaning a pilot in the air might believe there is something nearby that actually is not.
Mr. Lawrence and Mr. Luna have been helping to refurbish the equipment that solves these problems. They have to know how the radar inside is affected by the radome so they can adjust the equipment to solve the problem.
"The electrical test system measures these effects," Mr. Lawrence explains.
The radomes are tested in a large, electrically shielded, gray room. The walls, floor, ceiling, and most of the equipment inside are all covered with spiky gray foam, coated with carbon powder. The foam and carbon powder help to absorb radio frequency energy and other signals that can interfere with the testing process. Signals are sent through the radome to measure the deflections and alterations the radome causes.
All radomes have to be identical. They have to affect the sent-and-received signals the exact same way every time so the data can be accounted for. When testing is completed, and the effects have been characterized and identified by the Nose Radar Electrical Test System, the radome can be adjusted.
The Nose Radar Electrical Test System consists of six subsystems: the compact range, position controller, angle measurement system, antenna control unit, radio frequency source and measurement equipment, and computer control subsystem.
Every radome is first tested for consistency, then tuned and adjusted before it is deemed acceptable. Often it takes several tests, tunings and adjustments before passing the radome is possible. Adjustments and modifications can take time, and generally require the radomes to be sanded down or have material added to them to ensure they meet predetermined specifications, called performance curves.
The upgrade was necessary, due to outdated and obsolete equipment. At one time, two ranges operated under the old test system, but only one was operational due to the lack of parts and breaking down of equipment.
"It's hard to find parts and software for a computer that was built before DOS even existed," Mr. Lawrence explained.
Mr. Luna and Mr. Lawrence are nearing the end of the lengthy project. Mr. Luna, an Atlanta resident, has been away from home now for several weeks, and looks forward to the completion of their test system upgrades.
The Nose Radar Electrical Test System currently tests radomes on two separate ranges. The first range is completed and operational, and the first group of technicians has been trained to operate the new machinery. The two men expect to have the second range operational sometime in October.