Radio waves, traveling at the speed of light, have too much latency?

Oh you meant setting up a CDMA base station somewhere, faking a cell tower and controlling the drone that way? I misunderstood, that sounds like a practical and affordable solution that will surely escape detection and be better than a $50 handheld controller.

I wouldn't be so certain that setting up a fake cell tower would escape detection. You'd have people triangulating your position and preparing enormous fines as soon as you turned it on, well before controlling a drone with it.

Unless you were being sarcastic? It's hard to tell on the internet.

I was, yes. You're either using CDMA over the cell network so you can be far away, or you're using a $50 radio that has a 20 KM range itself.

No, I meant both the controller and drones radio use the CDMA modulation technique to transmit at power levels imperceptibly above the background noise levels. A listener would only hear white noise and would not even know the drone/controller are transmitting.

(This is after all what CDMA spread spectrum modulation was invented by Hedy Lamar for)

Absolutely nothing to do with the W-CDMA telephone system.

What's the transmission power for those? Current RC transmitters transmit at 10 mW or so.

Just above the noise floor of each frequency in the band at the time of transmission. Hence undetectable.