First the transmitter: the NRF code sends a very small packet of a couple of hundred microseconds, every 5ms, so Its utilisation of each channel is under 5% (MU ).
And the scanner: the NRF24 has no facility for RSSI, it can only tell us if the signal on any channel is above or below -64db, so its more of a "carrier/no carrier", yes or no signal. Martins code uses this to detect the amount of time any channel is in use, ie has an active carrier on it - it cant test the carriers signal strength.
So in combination we have a transmitter that transmits for only a tiny fraction of the timeslot, and a scanner that displays the amount of time a channel is occupied. I think this is why the peaks are much lower than say DSM2 or any high MU source like FASST
A high MU is good if you are the only one to have it - its not so good when everyone has high MU gear
Like everyone shouting in a noisy pub! Hence ETSI EN 300 328 V1.8.1. 2
just to be fair I didnt create anything, its 100% Martins code I only changed a couple of configuration options - asking for sprinkles doesn't make me a Gelatist
Cheers
Phil