One of the most difficult risks to manage with all sUAS flight operations, and in fact with most remote-controlled vehicle systems is radio interference. Detecting the threat and evading it is almost impossible without proper RF instrumentation, namely a decent spectrum analyser. It’s not something even developers are taking to the field too frequently, not unless RF measurements are the specific tasks for the day.
Operators are even less aware of the possible RF issues facing them out there, even though they are potentially flying in way more diverse areas than UAV builders. Of course, we can teach pilots to watch out for the signs like mobile phone towers and large dishes, but RFI doesn’t always have such visible sources out there. As the ISM frequencies mostly used by our birds are shared resources by definition, we must be able to check for potential interference in the target area.
We’ve developed a rugged docking field spectrum analyser module for our mission control stations (shown here: RHH link) that helps operators detect potential RFI issues early before take-off. It snaps right into the same RHH docking connector as our wedge RF boxes, and it has the same shape, but it houses a fast SA hardware, which can give you a full RF view up to 6GHz.
You can sweep your entire target spectrum on the embedded 10″ tablet of the RHH controller using both omni and highly directional antennas. Because it works as a standard USB peripheral device, we’ve also retained its functionality outside of our own rugged GCS system, so you can still connect it to a PC, tablet or even your smartphone.
Teaching most operators to use this tool may involve a bit of RF background information, too, but having them tune the SA to their work frequencies and watch for spikes around there is not rocket science. Reading the real-time, peak signal and waterfall displays is also slam dunk after less than 30 minutes of training. The better risk awareness and the early detection of RFI is worth the extra effort especially for critical UAV missions and in difficult environments.
Of course, there are many cheap RTL-SDR devices available that are capable of SA applications with the right software. Unfortunately, most of them aren’t fast enough, and they don’t go much above 1.7GHz, either, whereas we are especially interested in the 2.4GHz, 3.5GHz and 5.8GHz bands, as well. RTL-SDR dongles can still help you see your way around 430MHz, 868MHz and 900MHz, but they are also great tools for picking up ADS-B traffic, which is getting more and more important for UAV operations.

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