So spread spectrum technology is ubiquitous now in the 2.4GHz band. Is the technique specific to these higher frequencies due to some physical limitation?
That is, is it possible to have DSSS or FHSS in, say, the 72MHz band? I fly FPV using 2.4GHz and never fly more than a mile -- just too nervous about it. But I hear that 3 miles or 5 miles is a regular flight for the guys doing FPV in 72MHz band. I do realize that 2.4GHz is in the microwave band and it is highly suspectible to scattering just from moisture in the air -- we do use EM radiation in this band to cook food of course.
So the folks flying at 72MHz enjoy the benefits of super long range just from the physics of their radio waves. But I've always thought that if I were to fly miles away over some area where a random kid just gets his new RC aircraft toy for his birthday and just happens turn it on right on my channel then I'd get shot down for sure since his transmitter's location is much closer to my FPV plane and would be exponentially stronger than my transmitter's signal 3 miles away.
I don't understand why folks do not worry about getting shot down using FM radios for FPV. FPV flights go well beyond the boundaries of a normal flying club's field so frequency control is not available out there. But if we had DSSS or FHSS spread spectrum in the FM bands then it would be FPV nirvana.