Having read through a lot of discourse on antennae, there are two questions whose answers I haven't spotted thus far, so I might as well ask them together in this post.
If I understand the general consensus about 2.4GHz antenna carrying the incoming video signal from the drone, omni-directional antennae with gains of 8 dBi or or 9 dBi are preferable to those rated for 12dBi or 15dBi, because the higher gain antennae are "more directional" than the lower gain antennae, whose signal reception pattern is described as more evenly dispersed, and less focused.
With no background in microwave theory, my expectation that a higher gain antenna would pick up video signals from the drone over greater distances, is apparently incorrect. Intuitively I'd have picked a pair of 12dBi antennae over a cheaper pair of 9 dBi antenna, going by my previously held perception that more power is always better, from a purely technical standpoint when it comes to both transmission and reception of radio signals.
My question is therefore, how it is that a 15 dBi, 2.4GHz antenna is classified as being "too directional", despite being of very similar physical shape to a 9dBi, 2.4 GHz antenna, that is regarded as "less directional" in comparison. My limited understanding of antenna design, is that the radiation patterns are determined largely by the geometry of the antenna, so this difference in receptivity patterns is difficult to understand, for me, given the close similarity between the two "whip" antennae rated for 2.4GHz but with different gain ratings.
In short, will a pair of 15dBi, 2.4GHz antenna for video reception from my Phantom 3 Standard, powered by a pair of line amplifiers to address signal attenuation due to coax cable lengths for a roof or mast installation, fail abysmally as long range video receiver antennae for 2.4GHz, or would such a setup just prove slightly less effective than a pair of 9dBi, 2.4GHz antenna ?
My second question is that in looking over many of the antenna pictures published in this forum, I generally see the twin 2.4GHz antenna for incoming video reception, yet rarely see that third antenna for the outgoing 5.8GHz control signal. I got to wondering if best practice in mast or roof-mounted antenna placement, requires a pronounced separation between the 2.4GHz antennae pair, and the 5.8GHz control signal antenna.
On the Phantom 3 Standard controller, all three antenna for both frequencies, are side by side, so I would be grateful if anyone can find a moment to explain whether or not the 2.4GHz and 5.8GHZ antenna need to be moved further apart when they are amplified, to prevent signal interference between the video and control links. Apologies for the long-winded questions here, but I was reaching the point where the more I read on the subject, the less certain I became on the subject of antenna selection for my ongoing mast mount project.