I am building a drone to achieve the range of 10km. Is there any drawbacks if I run a 5.8GHZ on my VTX system and 900MHZ for my crossfire radio link system? I know having a 900MHZ radio system will achieve the range but does the same thing apply for VTX system if I decide to run 1000mW poweroutput and strong gain antenna? Right now I kind of doubt that the 5.8GHZ for 10km mission.

I am trying to do ardupilot + fpv

Assuming you are flying 10km line of sight without any direct obstructions in a relatively open area like in the middle of no where with a very low noise floor (not in the City center or near a dense housing area) then 5.8Ghz should be capable of providing you a reasonable video signal (with the right output power and antennas).

Same goes with Cross fire at 900Mhz. And most of the quads on this forum are running the same setup.

Your most important task is antenna choice and placement.

For Crossfire you need the antenna mounted vertically away from the quad and fly with your transmitter with the antenna vertical. Something like a TrueRC Barpole will do well or else you can make your own by following this thread: https://intofpv.com/t-how-to-make-your-o...rx-antenna

Same goes with the VTX antenna, you need something with a tall stalk high away from the quad.

Something like this with the vertical vtx and crossfire antennas at the rear (ignore the immortal T in front since this quad is running a Crossfire Diversity RX): 



On your goggles you are going to need a helical antenna (the longer the better with more turns for killer penetration 



Watch FalconRad FPV's video for understanding his setup:

(05-Aug-2021, 10:11 AM)kafie1980 Wrote: Assuming you are flying 10km line of sight without any direct obstructions in a relatively open area like in the middle of no where with a very low noise floor (not in the City center or near a dense housing area) then 5.8Ghz should be capable of providing you a reasonable video signal (with the right output power and antennas).

Same goes with Cross fire at 900Mhz. And most of the quads on this forum are running the same setup.

Your most important task is antenna choice and placement.

For Crossfire you need the antenna mounted vertically away from the quad and fly with your transmitter with the antenna vertical. Something like a TrueRC Barpole will do well or else you can make your own by following this thread: https://intofpv.com/t-how-to-make-your-o...rx-antenna

Same goes with the VTX antenna, you need something with a tall stalk high away from the quad.

Something like this with the vertical vtx and crossfire antennas at the rear (ignore the immortal T in front since this quad is running a Crossfire Diversity RX): 



On your goggles you are going to need a helical antenna (the longer the better with more turns for killer penetration 



Watch FalconRad FPV's video for understanding his setup:

Thank you so much for your insight! The mission of my drone is to climb the  slope of a Volcano in Mexico to drop multiple payloads on the volcano sides with fully autonmous system but if anything happens the operator will still be able to ovveride the autopilot and complete mission.  This would mean we will be having multiple trips.
One challenge that we faced right now is that we have to drop one payload behind the volcano which means beyond the line of sight. From what I research , we might have to use something like this: https://uavionix.com/products/microlink/. But I would like to ask whether if there is any other options for FPV BVLOS?

Thanks!

Ardupilot makes this pretty easy. Waypoints, heading hold, altitude hold really help get you past any video issues you might run into.

Setting up telemetry and using hud helps keep you flying the right direction if video drops out too.

I use the yaapu script to put the telemetry data on my t16 transmitter screen so I can just lift the goggles and keep flying from there. Latency is pretty bad with the telemetry on the hud so smooth on the sticks and your good to go. Ground station is convenient if you drop video and navigate with telemetry, you can easily keep an eye on the video screen for when the video is recovered. If everything goes wrong activate return to home.

Why stop at 1000mw. Why not 5000mw? 9000mw?
Higher power is not better. More signal multipath. More noise.

In a perfect world... you could just use the best technology. The best frequency. Big budget.

Basically the military.
ie fly/control drone 300km away

Need to research RF basics like link budget, noise floor and convolution.

Cell phone can send 150MBps+, and has 30km+ range. You dont see giant helical antenna sticking out?
Its always tradeoff in $$$, latency, bandwidth, range.