I used spektrum for years, when I moved to HK I left all of my stuff in the UK for my dad to use (aren't I generous). When I started racing again in HK I bought an Esprit 3 with a KO 901S module and a KR408S receiver. It has caused me no end of problems. At meetings here there can be 20+ people practicing at the same time, the only way I could get the receiver to bind to the transmitter was to walk away from the rostrum, out the car park and down the road, switch everything back on and then walk back to the track.
I complained to KO, and returned the module and receiver to them. They updated the transmitter module to a version with a blue pcb inside. Unfortunately; as I found out at the next race meeting, this did not fix the problem.
In the end I gave up and bought a new spektrum module and receiver with which I haven't had a single problem, good job rc stuff tends to be cheaper here
The KO equipment is sat on my desk doing a good job pretending to be a paperweight. To be honest I don't know what else to do with it. I'm not going to use it and I don't want to sell it to somebody knowing that it doesn't work correctly. (it works fine when no other transmitters are around).
I hate to bad mouth things but that's been my experience with KO 2.4