Approach and Training

An Anti-Jam Approach

When evaluating anti-jam systems that can defeat simultaneous jammers, a simple rule of thumb to remember is that a CRPA can null in n-1 directions where n is the number of elements. So a 7-element system can null in 6 directions and so on.

Soar says, “The real proof of anti-jamming effectiveness is in the application. If an anti-jamming system shows promise, test it. Evaluate how it works in critical situations and verify ease of use and accuracy.”

Don't Neglect Training!

Training often gets overlooked when it comes to the use of GPS systems. For instance, users need to learn what jamming can do to their systems and practice the mitigation methods so that their responses to alerts are spontaneous, just like any other drill.

Consider the following point. Intuition would generally suggest that the user elevate the antenna when a communication signal is lost—but with GPS, the opposite is typically the case. Since jammers are usually on the horizon, a more effective response might be to place the GPS receiver on the ground or even in a shallow hole, or hold it so that your body or a vehicle is between you and the jammer.

Some receivers flash the same message—“jamming detected”—when the antenna loses signal, even though the problem might be that the user has moved indoors. Exposure to jamming as well as moving the GPS receiver in complex environments will give users the experience to judge between the scenarios.

Setting up jamming for training used to be complex and time consuming. But now authorized users, with appropriate permissions in place, can take advantage of the NAVWAR Electronic Attack Trainer (NEAT) designed by Defence Research and Development Canada and built by NovAtel. NEAT is a simple handheld unit that emits a variety of low power signals.