RE: 2.4 GHz vs 72 MHz - Free space loss
This is an interesting suject to me.
I used to be a electro-magnetic compatibility test technician for automotive components. And as a general observation, the higher the freq the lower power was needed to generate the same RF field (volts per Meter). But the signal strength decreases more over a distance than lower frequencies (Free Space Loss)
The Fresnel Zone is independent of frequency and is determined by distance ( i.e. Curvature of the earth and line of site. So there should be no difference between the 72MHz and 2.4GHz frequencies.
The main thing to remember is the noise floor at any given time for the two frequencies. The rule of thumb is the higher the frequency the lower the noise floor. When we did free range testing (open air - - outside of the Anechoic Chamber) the noise floor was greatly reduced at frequencies above 1.6GHz. The natural harmonics of lower fundamental frequencies lose lots of power the further they are away from the fundamental freqs.
A good example of the noise floor is we have two rooms Room A and Room B
Room A is 72MHz and Room B is 2.4GHz
Two people are trying to have a conversation with each other accross in Room A and Two people are trying to have a conversation with each other accross in Room B.
In room A there are 450 other people having idle chit chat, like at a wedding after the drinks have been flowing for a while. The two people have to yell and may not even hear each other.
In Room B ther are 10 other people whispering and the two original people can talk with out yelling.
The free space loss in 2.4GHz is there but you don't need the excess power that you do in 72MHz to overcome the noise floor.
Not to mention the data transmission bandwidth increases by over 30 times (faster servo response times, possibly increased sensitivity in future servos).
But all in all I think this will be good for the hobby.