Drone Jammers – a problem?


A recent article in Make Magazine described how to make a drone jammer using a Raspberry Pi and a DIY cantenna.  The jammer in the article, while illegal to use, is unlikely to work because of the low power of the Pi WiFi.

In order to disrupt the control of a drone you have to overwhelm the flight control receiver in the aircraft with a really strong signal. (The technical term to Google is “desense”). If just transmitting on the same frequency were enough to disrupt communications, then can you explain how hundreds of teenagers at a concert can use their cellphones to tweet about the entertainment, all on the same cellphone frequency bands. The microwave control link used in drones is that robust.

The aim with the cantenna in this article has to be very precise, and you have to be closer to the aircraft than the controller. As soon as the aim from the cantena is off by a few degrees, the controller resumes control.

Most drones that use a 2.4 GHz control link have to lose the signal for a preset time before deciding that it needs to go into a failsafe mode. Usually one or two seconds. This accommodates the occasional signal dropout that is normal in controller-aircraft links. It’s not unlike listening to a weak FM radio station in your car that is occasionally interrupted with a burst of static.

If the aircraft is flying a pre-programmed route, such as in a land survey flight, the aircraft is not depending on maintaining a control link. It will continue to fly the programmed route even if the controller is switched off.

As with most other “anti drone” technology, besides being illegal to use, it’s unlikely to work except in very controlled conditions and with a very small subset of drones.

Notwithstanding that interfering with an aircraft in flight is a federal offense (18 U.S. Code § 32), there will always be venture capital money to throw at a non-existent problem.

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