What Distance Can You Detect Drones From (or anything airborne for that matter)?

One of the most frequently-asked questions when discussing our RF drone detection system is: “At what distance are you able to detect drones? How far away can they be and still be picked up by RFeye?” And the answer, as is so often the case, is “it’s complicated” – depending on the conditions, the answer could be anything from many kilometers to tens of meters. So let’s see if we can break it down a little further, and explain a bit more about the factors that affect drone detection distance, and what kind of performance is achievable in the real world.

It’s worth pointing out that for the purposes of this blog, when we refer to drones, we are typically talking about small COTS (commercial-off-the-shelf), or Category 1 drones; these systems will almost invariably be controlled from the ground, so there will be two signals that we can potentially locate: the downlink signal from the drone, and the uplink control signal from the controller on the ground. The downlink usually has narrowband telemetry bursts for guidance, and a wideband video link signal. These signals are often seen in 2.4GHz or 5GHz frequencies, but can also appear on 900MHz as well for certain activity.

Knowing Your Target

As we mentioned earlier in this blog, the primary focus is on COTS drones, such as those manufactured by DJI. Even within these kinds of drones that typically operate within the ISM band, the amount of power these drones will be allowed to transmit on will be largely impacted by the country’s regulatory body:

Regulatory BodyAuthorized Transmit Power (in mW)Signal Strength (in dBm)United States25mW~13 dBmUnited Kingdom100mW~20 dBmEurope50mW – 300mW~16dBm – ~24dBm

So, even if the deployed RF detection system has good detection range in one country, it may not necessarily work as well in another country depending on the authorized transmission power of each drone. Frequency also has an influence on the detection range as well; signals at a lower frequency will be detected farther out than signals on higher frequencies, as illustrated below:

Interfering Signals

The other major consideration when determining drone detection range is the effect of other signals at the same frequency. Most commercial off-the-shelf drones work in the Wi-Fi bands (2.4 GHz or 5.8GHz), so will be subject to interference from the multitude of WiFi/bluetooth signals permanently being broadcast. In situations where, for example, a wireless access point is significantly closer to the receivers than the drone, it may be impossible to pick out the drone signal from the background noise created. This will be particularly true in dense urban settings. RFeye DroneDefense software can mitigate the effects of this interference with its inbuilt WiFi and Bluetooth reject features, which can identify these signal types by analysis of their keying features, and essentially blacklist them from the analysis. This allows the system to perform drone detection even in busier RF environments.

Conclusion

However hard troops try to disguise their electromagnetic signal, whether by using advances in technology, natural features, and terrain or by deception, there will be people on the other side trying just as hard to detect and geolocate them. By testing and evaluating TTPs on the training ground, troops will have more confidence that the methods they are employing will be effective. This can be achieved by installing a network of IIO Technologies receivers in and around military training grounds. Signals can be detected, geolocated, and recorded so that troops can experiment with different methods and learn in a realistic training environment. Our solutions are TRL9 and easily procured through multiple DOD contracting pathways, both CONUS and OCONUS.

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