RMILEC UHF RC for FPV - why only 1Km range?

After the rather poor performance of the RMILEC UHF RC system in my last video, I thought I'd check and make sure that there was nothing on the model causing too much RF noise on the 433MHz band.
As you can see, turning on the FPV backpack with its Sony 600TVL camera and 200mW 5.8GHz transmitter barely altered the noise floor -- although there was a very small peak down at about 410MHz (too far away to be of any consequence).
As you can also see, there are a couple of noise spikes at roughly 429MHz and 430MHz but these are also outside the operating frequency of the RMILEC gear so should not cause problems. The amplitude of the noise is greater outside the workshop so it is possible that they are coming from the area where the lockouts were experienced. However, being more than 3MHz off the operating frequency of the RMILEC system, they should not affect its operation even if they were much stronger in intensity.
Stay tuned and I'll see if I can find out why the RMILEC only offers 1Km of range in my flying environment.
And stay tuned for the upcoming review/comparison of the Dragon Link UHF RC system.