Lesson about antenna placement

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Hey everyone!

While I have yet to reach pro status like some of you guys here I’ve spent hours educating myself and consider myself now to be a great pilot. I recently came across something that I must admit I did not know. I think it’s easy to assume one can just pull out the antennas on a DJI remote and it just works without considering the technology behind it.

I’m hoping this video will teach some of us something about antenna placement and signal direction. I was so concerned about trying to fly well that I forgot to educate myself on the minor details that are just as important. Just goes to show whether in a hobby/career or in life there’s always something to learn no matter how skilled one might believe they are.

Fly safe y’all


 

mostly_tacos

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Good video. I spent a long time as an enterprise network engineer, and a lot of tme working on wireless at 2.4 and 5ghz. The same points apply to WiFi in your home or at work. People don’t realize that WiFi signal kind of makes a donut from the antenna, assuming an omnidirectional antenna.

That’s also how the parabolic antenna ”range extenders” work. You’re sacrificing signal strength behind the convex reflector to “boost” the signal on the other front side.
 
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Thank You ron-ep,
Are there any early warnings that signal strength is being diminished to the aircraft? I have never flown the aircraft to any great distance (1/2 mile maybe). I would assume that the video signal would be affected and perhaps flight controls may lag a bit. Anything else?
And "mostly-tacos" mentioned the parabolic antenna range extenders. I know I have only flow short distances but would like to know what percentage increase in range is possible with them - given clear, unobstructed views and calm conditions. I live in the southwest and photograph geologic structures with a P4P.
Thanks for the well done and clearly explained video. I look forward to viewing your other videos.
 
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mostly_tacos

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That's a DJI video from DJI's website. You can see several more, there.

If you're seeing image degradation or lag, you're at the limit of the flight and should bring your quad back. The signal strength indicator on your monitor is the best bet. I think you can find more detailed signal statistics, but I haven't poked around to find it. I may try to this afternoon, and if I can find it, I'll post here.

The range extenders are a mixed bag. Some work well, some don't. Almost all need pretty specific working conditions. Although, admittedly, I'm drawing from my experience with wifi, not specifically UAV. Back in the day, we'd make wifi range extenders with Pringles cans. ;-) I'm assuming the concept is the same, and it has a fairly narrow positioning band and signal falls off the table if you're outside the band.
 
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Thank You ron-ep,
Are there any early warnings that signal strength is being diminished to the aircraft? I have never flown the aircraft to any great distance (1/2 mile maybe). I would assume that the video signal would be affected and perhaps flight controls may lag a bit. Anything else?
And "mostly-tacos" mentioned the parabolic antenna range extenders. I know I have only flow short distances but would like to know what percentage increase in range is possible with them - given clear, unobstructed views and calm conditions. I live in the southwest and photograph geologic structures with a P4P.
Thanks for the well done and clearly explained video. I look forward to viewing your other videos.

I can’t say I’ve ever flown further than 1 mile. Just not my style of flying currently. I fly at the beach a lot so there’s no interference there. I too have a taco style range extender and I’ve had no issues with it so far. I can say however due to my lack of knowledge in this area that I do recall as I went further out I would get a little bit of break up in video feed. Only for a second though. I now know that it’s because of how I placed my antennas. I thought aiming them towards the aircraft was best when in fact they should’ve been straight up as shown in the video.
 
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Thank You ron-ep,
Are there any early warnings that signal strength is being diminished to the aircraft? I have never flown the aircraft to any great distance (1/2 mile maybe). I would assume that the video signal would be affected and perhaps flight controls may lag a bit. Anything else?
And "mostly-tacos" mentioned the parabolic antenna range extenders. I know I have only flow short distances but would like to know what percentage increase in range is possible with them - given clear, unobstructed views and calm conditions. I live in the southwest and photograph geologic structures with a P4P.
Thanks for the well done and clearly explained video. I look forward to viewing your other videos.

I usually gauge it by poor or broken video feed. Again, I don’t go far so I dont push it to any limits like that.
 
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Thanks for the informative video! I too have been pointing the antennae directly at the drone thinking that was correct. That explains my video breaking up occasionally. (I'm no "pro", just an old photographer messing around with drones!) :)
 
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If interested in antenna performance, get your ham radio license and you’ll learn a lot along the way. Seven year old kids have gotten ham radio licenses, so it’s not that tough.

Interestingly, high-gain antennas and so called range extenders generally don’t increase the power of the transmitted or received signal the way you may think. They typically distort or focus the available signal, which strengthens the signal pattern in some or one direction while weakening or eliminating the signal in other directions. So if you opt for a highly directional antenna, like a parabolic reflector, you better keep the tightly focused pattern “pointed” directly at the drone with no obstructions for best results. For a stock antenna or one with a parabolic reflector, the drone should be perpendicular to the antenna - not off the end of the antenna.

One benefit of non-high-gain antennas is their transmission/reception patterns tend to be less tightly focused and more omnidirectional. Consequently, they are more able to use reflected signals that are not on a direct line to the drone than more tightly focused highgain antennas. So, a low-gain antenna may perform better in an urban environment where the signal has plenty of opportunity to bounce off of stuff than a high-gain antenna that is focused in one direction and not able to receive reflected signals.

Finally, if you fly within the law with respect to VLOS, the stock antennas, used properly, are all you need. If you feel that you need higher gain antennas, it’s likely that you are not using the stock antennas properly, or you are flying beyond VLOS, or maybe in a noisy RF environment.
 
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Yep.

1596384184230.png


For really far flights I use these:
1596384341504.png


D
 
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Yep.

View attachment 119594

For really far flights I use these:
View attachment 119595

D

Yes, elevating your antenna is good too.

I don’t recall the power in Watts at which DJI UAVs operate, but I’ve communicated with the ISS, which was hundreds of miles away, using a 5-Watt VHF HT (Ham Radio for handheld walkie-talkie), which demonstrates how well elevating your antenna can work (the ISS’s antenna was 200-miles high). This also demonstrates why the FCC and FAA don’t permit people to transmit on an aircraft band radio outside of an airplane; i.e., from the ground, without a license (unless it's a human life or death emergency).
 
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