Part 107 UAS pilot reported a lost link during a flight. The reporter stated they believe the lost link may have been caused by possible jamming or counter UAS technology.

Narrative

I was in the area and decided to take my drone to capture some sunset photos of the skyline. I researched the area fully and completely both several days prior to the trip and the day of the trip. I recognized that it was an area where there were several no-fly zones. I first recognized that it was part of the special flight rules area for Washington; DC. I measured out and confirmed that it was in the outer ring; 15 to 30 miles; where flights below 400 feet were authorized if they were compliant with regulations. There were also four DOD non fly areas. I ensured that my launch point and flight path would not take me over any of those facilities.I launched from my launch point which was at Location A. This would allow me to keep visible line of sight of the drone and ensure that I did not fly over any boats navigating in and out of the harbor. I did a full systems checkout of the drone prior to launch. I ensured that all navigational databases were up to date and that it had the latest firmware. Since it was at dusk; I also had the drone equipped with its strobe lights and port and starboard orientation lights. This was a well-researched and fully compliant flight.I launched at XA:01 PM and proceeded to take position for a sunset around XA:13. Having set up my lateral alignment of the sun with the town; I began descending to get the perfect vertical profile for the photo shoot. It was at this moment; approximately 6 minutes into the flight; that the drone went lost link. I could not tell whether or not the drone was receiving a signal from the control system; so I pressed the return to home button. Visually; I could tell from the strobes that the drone was still stationary. So; I impatiently waited for the lost signal timeout feature to establish a return-to-home (RTH) profile. Fortunately; the drone executed an RTH as advertised. As the drone got closer; I kept trying to reestablish the link and take control of the drone; but it was not responding. When the drone started its descent for landing; I noticed that there was an offset in its home point and that the drone was about to auto land where some innocent bystanders were standing. Immediately; I walked over to the innocent bystanders and politely asked them to step back. I tried one more time before the drone landed to establish control of the UAS. It would not do so. The drone landed without incident and shut down. I powered down and re-powered the drone and my base station and could not reestablish the link. I decided to do a hard shutdown of the drone by swapping out the batteries. Again; I could not reestablish a link. Then; almost exactly 5 minutes after the original flight had lost link; communications were reestablished with the drone as if somebody had turned off a switch. I was not touching any controls or software controls at the time that link was reestablished. I executed a second flight as a test flight and had no issues. I continued out to a position near where I was before; but not as close to any of the facilities and had no issues.All the symptoms of the first flight matched what could be experienced if a Counter UAS (C-UAS) system on a facility had jammed the radio frequency; including the way that communications were eventually reestablished; as if somebody had turned off a switch. I cannot prove that a station jammed my radio frequency. However; it is very suspicious. I have verified and re-verified through post-flight data that at no time did my drone fly through any no-fly areas. My closest point of approach to one facility was .1 miles. My closest approach to another facility was .3 miles. The airspace was Class G airspace with no restrictions.I would like to know whether a facility activated its C-UAS system on that evening. If they did; they induced a hazard to aviation safety. First; there was the fact that I had no control over the UAS when it did its RTH and that I had to ask innocent bystanders to step away from the area where the dronewas returning to. Second; when a drone loses its link; it becomes unpredictable and uncontrollable. I could have had a flyaway that could have harmed citizens. I was not far distant from many populated areas; on a night where there was an event going on. I did not go anywhere near the event; but it would have been within range of the drone had it had a fly away. If a facility is activating counter UAS equipment on drones that are not in the no-fly zone; and not showing hostile intent; they are creating a hazard to aviation safety. They need to be instructed to cease such activities if they are doing it. Once again; I cannot prove anything. But my system has been incredibly reliable in the past. I have never lost a link with this system; yet. I was well within range of my equipment and had no obstructions between me and the drone. Post-flight data shows 100% signal strength right up to the point where there was loss of link. I have not had any other indications of equipment failure on any other flight since this flight. This is highly suspicious of jamming. I would like to know if there are any additional steps I need to take in the future to prevent being jammed; if that is what occurred. I plan to return for sunset photos again.