Antenna jungle - inventory - What's out there?

Building a mast for my dad. 2" pvc pipe seems much better, more rigid. L-Com 8.5's direct out of RF-Linx 1.5 watt. amps. 10-15ft tall. 50ft LMR-400 coax. Boxes are water tight. This is the top assembly that fits onto the mast pipe.
20170423_182523.jpg
 
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.
 
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.
I wasn't aware that a P3S controller had any 5.8Ghz frequency available to it. The availability of the 5.8Ghz band was only added in the P4P and the Mavics. All prior aircraft were strictly 2.4Ghz.
 
Yes sir, the 5.8GHz carries the outbound control signal for the Phantom 3S. Having read a few references to possible interference between the 2.4GHz and 5.8GHz antenna, my novice speculation is that for mast and rooftop installations, the two antenna types are placed far apart so as to reduce the odds of such cross-talk between their amplified signals.

I just found it odd that I didn't spot any 5.8GHz antenna in all the roof-top and mast installations whose photos have appeared in both forums that address the elevated placement of antenna . Even if the two types of antenna were required to be located far from each other on separate masts, I've only ever seen pictures of one mast, hence my wondering about the exact location of that 5.8GHz whip antenna.
 

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For anyone out there that is still tinkering with antenna options for their drone, I would like to draw attention to the All About Circuits forum, whose contributors are very well informed on the subject of RF theory, and would be in a position to address virtually all questions relating to this esoteric filed that is akin to alchemy, for this rank novice.

 

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