RE: 2.4 GHz vs 72 MHz - Free space loss
You know that higher propagation loss for 2.4 GHz vrs. 72 MHz is a two edge sword. Yes, we might need the processing gain to have hihge receiver sensitivity, but ther eis another very good side! Namely. isolation from interference generated remotely from our flying site! This is the basic principal of frequency reuse that is applied in AM, FM and TV broadcast as well as cellular telephony. Becasue of these extra losses we are flying around in a nice local bubble relatively safe from same frequency transmission from the next county or next park.
Loss can be a good thing!