This seems to be a question that is asked, but never really answered. The normal response is a full range receiver has enough range to work as far as you can see the plane. This was correct, but more recently we have been flying FPV which has allowed us to explore this question further, and with the GPS overlays have a reasonably accurate idea of the answer.
We have had 3 incidents which I based this post on, the first was the balsa E-Fair glider which was posted about here:
An AR400 full range receiver was installed in the glider which was correctly range tested to over 40 paces. At about 1 minute 10 seconds into the second flight control was temporarily lost, from the GPS coordinates this was calculated to be a little over 500 meters from the landing point.
The second example was a new video which was a flight of my polystyrene Catalina containing an AR6210 full range receiver (genuine not Chinese fakes which are about at the moment and correctly range tested):
At about 1 minute 19 seconds into the video control was temporarily lost, although the overlay data is not on this video since it was recorded on the camera not the ground station the distance from the landing strip was a little short of 1600 feet (somewhere just over 500 meters)
The third incident is a little less clear. It is Scott’s balsa Decathlon flight. This contained an Orange DSMX 8 channel full range receiver:
Although the wind was blowing the plane away from the strip and the video was lost here which means that there is no direct evidence that the control was lost this was at around 1600 feet from the strip.
So the range of a standard Spektrum DSM based full range receiver appears to be about 500 meters. When flying FPV the pilot does not point towards the plane, so the orientation of the transmitter aerial will not be optimal, and in both cases where control comes back, the plane rotates then control returns, so the direction of polarization of the signal also appears to be taking an effect. We have also seen a notable drop in range of the FPV video gear when it was fully contain within even a foam plane, so perhaps the range could be extended slightly by externalizing the antennas. It is also possible that interference has caused these radio brownouts, we have seen brownouts before, but since both of these control losses happened at about the same distance in opposite directions from the strip, this offers less credence to this theory. Even with all these considerations I cannot see them extending the range to 1Km or more as I have see quoted on the internet. For normal flight 500 meters appears to be about the range of vision to reasonably see and control what your plane is doing. Our 250mw FPV gear with circular polarised antennas also appears to have about this as a range, higher powered FPV gear may need longer range control radios.