That's my thought as well, but you never know when it comes to legal and regulatory stuff...
;-)
TCS
Arc V and Odd Observation
- Thread starter Chaosrider
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;-)
TCS
Yesterday I did some experimentation at the ragged edge of the controller range. Out to 3000 ft, the signal shows 5 bars consistently. But once it drops down to 4, it takes very little additional distance to get it to drop down to 3, and turn red. The steepness of that decay curve is a big part of my hesitation about pushing any farther.
The rapid degradation was repeatable, and when I'd back off sometimes as little as 100 ft, I'd get at least the 4 bars back. It's a much sharper edge than I would have expected.
TCS
It's not so much the launch site that affects control range, but more where the controller is. Once the drone is airborne the actual launch site becomes irrelevant for signal strength. I guess you were standing next to the drone when it took off, and stayed there for the duration of the flight? Moving the controller location can heavily influence control range - eg step out from behind a tree and the useful range in that direction is hugely increased.
I have a mini 1 which can have a control range of less than VLOS, especially on 5.8ghz. Understanding what the drone will do on signal loss is very helpful as I can easily fly out of signal range. I have had numerous times when I've lost signal and auto RTH has been initiated. Here are the things that I like to be aware of long before signal is lost:
- Current RTH settings (RTH altitude and current home point - this can be moved during flight if you wish)
- Wind direction and speed. This is a big issue for the mini 1, due to its limited power, but could catch out more powerful drones on a windy day.
- Knowing approximately where the drone is relative to me and the surrounding landscape
- What obstacles may be in the projected flight path as the drone does its RTH
- What obstacles will be in the signal path between the controller and drone as the drone does its RTH.
In a flat field or where the radios are well above the terrain, no buildings or trees and no antennae, and with adequate altitude, the 10 plus km range is very real. A single tree along the radio path will affect the link range. But there are enough "range test" videos out there to know the DJI spec is real; and if you look at them closely, all are starting from an elevated point, flying at a reasonable altitude, straight and level away from launch point. In many tests, the operator swings the controller such that the antennas no longer point at the drone and LOS occurs (signal drops like a rock).
The worst way to infer range is to sit in a bowl, a small clearing with trees or buildings all around, and try to see how far the radios will work. Launching in a neighborhood park is bad for range.
That said, with my HS 720 video feed is lost well before 1000 feet, but it can fly out about 2250' over farmland before it loses control signal and does its RTH. My Air 2 / RM500 radios perform much better, but 2500' is about my physical visual limit for being able to say I can see my drone, and I know for a fact I wouldn't be able to tell you which direction it was pointing - by definition that is beyond FAA VLOS - and I have rather good visual acuity.
So I guess it comes back to what exactly are you trying to learn about your drone? Will RTH work when you need it to? Or, as the discussion seems to be trending, will it fly away from you for 15 minutes before returning home?
I see you are in Nevada - like Idaho - lots of places where there is nothing but dirt and sage for dozens of miles. Drive out into the desert, find a straight dirt road across a valley. Power up the drone and controller, place the drone on a plastic card table leaving it powered and ready to fly, then drive off a mile. See if you are still getting video. Then do a gimbal move to see if the telemetry is working. If a mile works, drive out to 2 miles. Rinse and repeat until telemetry fails. You then know your radio range. Since the drone is not flying, no chance of an erroneous RTH, and no VLOS violations, either.
The worst way to infer range is to sit in a bowl, a small clearing with trees or buildings all around, and try to see how far the radios will work. Launching in a neighborhood park is bad for range.
That said, with my HS 720 video feed is lost well before 1000 feet, but it can fly out about 2250' over farmland before it loses control signal and does its RTH. My Air 2 / RM500 radios perform much better, but 2500' is about my physical visual limit for being able to say I can see my drone, and I know for a fact I wouldn't be able to tell you which direction it was pointing - by definition that is beyond FAA VLOS - and I have rather good visual acuity.
So I guess it comes back to what exactly are you trying to learn about your drone? Will RTH work when you need it to? Or, as the discussion seems to be trending, will it fly away from you for 15 minutes before returning home?
I see you are in Nevada - like Idaho - lots of places where there is nothing but dirt and sage for dozens of miles. Drive out into the desert, find a straight dirt road across a valley. Power up the drone and controller, place the drone on a plastic card table leaving it powered and ready to fly, then drive off a mile. See if you are still getting video. Then do a gimbal move to see if the telemetry is working. If a mile works, drive out to 2 miles. Rinse and repeat until telemetry fails. You then know your radio range. Since the drone is not flying, no chance of an erroneous RTH, and no VLOS violations, either.
Lots of drone pilots seem to think that the RF energy going between their controller and the drone is simply a straight line of sight situation. It isn't. Whatever is directly between you and the drone is only part of the picture. Objects, structure, and terrain all around you ... including behind you and to the sides between you and the drone ... all can affect the signal level. Reflections and refractions from just about anything and everything can interact with the direct path to form interference patterns that either enhance or diminish the strength of the signal that the drone sees. The possible combinations are almost considerable and difficult to predict, although that is exactly what the software that calculates Fresnel Zones tries to do.
Most of the time the direct path is strong enough to override the other influences, but not always. In your case, standing in a cup shaped hollow at the rear deck might be causing the RF that gets transmitted behind you to reflect and negatively combine with the desired energy headed forward. The distant ridge could also cause an unwanted combination of signals that is less of an issue from the front deck but more of an issue from the back deck due to the longer path length (which affects phase), but my money says the cup shaped hollow is the more likely culprit.
A while back there was a thread here about a guy who flew his drone out some distance to make a loop around a large water tower. While still being in direct VLOS he suddently and completely lost control as the drone made the turn around the far side of the water tower ... almost certainly a case of a reflection off the steel dome of the tower negatively combining with the direct path.
This stuff can get very complicated and is MUCH different than the wide open spaces that DJI and everyone else reference when they talk about a control range "up to" some stated distance. DJI isn't wrong when they say that, and they have no way at all to predict what range anyone will see in any random situation.
The three to four bar switchover is binary. That fourth bar is either on or off. So of course it is a "sharp edge." The same is true of one to two bars, four to five bars, etc. You are chasing rainbows when thinking these sorts of electro-optical delusions are real.
LOL - you need to get out and fly your drone and enjoy it.
Good advice. I'll have to concoct a trajectory where there's at least some chance that I'll be able to recover the drone if the lost signal RTH doesn't respond correctly. That's not so easy to do where I am, but I'll do it incrementally. Down the creek is clearly the right direction to maximize recovery options.
I think the next time I try this, I'm going to go ahead out to only 2 bars of RC signal, and just hover around at that distance for a while. I'll do that a couple of times before I push on out to just 1 bar. After that, push it to signal loss.
It's a test worth doing, thanks!
TCS
This is a good point that I hadn't considered. I do lie in a canyon, which is a lot like a bowl in the sense your describing. Probably even worse than a bowl for signal distortion, because there's no symmetry at all in the terrain.
Makes sense, thanks!
TCS
This is very helpful. I had forgotten most of the RF physics that I used to know, but the picture is starting to form now in my head.
Thx!
TCS
I get out and fly whenever time and weather permit!
I think I may have described the signal degradation that I saw poorly. 5 bars means "above level X". I understand the binary nature of moving from above X to below X. What surprised me was how little additional distance it took to make it drop to 3 bars from 4. What that said to me was that the distance it took to go from 4 to 3 is probably comparable to the distance to go from 3 to 2, and I was seriously not interested in doing that.
I wasn't chasing any rainbow, and I have no idea what delusion you think I had, that wasn't real. That whole sentence is weird, and doesn't make sense to me. I was just trying to understand the implications of my observations in real time, and decide what to do about it.
My decision was to come home.
Thx,
TCS
RF propagates weirdly. It is not linear as you might casually expect. Reflected RF can mix with the primary waves and cause peaks, nulls and voids in the signal. So the drone will fly through these peaks and voids and the signal strength can and will vary dramatically. Think interference patterns in pond ripples.
As for the meter, you wouldn't be the first person who believes they see a pattern in low resolution digital signal strength meters. Hysteresis in the meter can cause the eye to see all sorts of things that really aren't there. My choice of "rainbow" and "delusion" to describe the effect was for humor - probably a bad choice. Maybe red herring would have been better.
It shouldn't be a surprise to see your signal strength go from 5 down to 3 then later back up to 4 or even 5. This is just what radio waves do. On the other hand, if you are in a perfect setting, no hills, trees, buildings, powerlines, antennas of any sort for several miles, you might get a clean propagation where the signal falls off according to the rules.
As for the meter, you wouldn't be the first person who believes they see a pattern in low resolution digital signal strength meters. Hysteresis in the meter can cause the eye to see all sorts of things that really aren't there. My choice of "rainbow" and "delusion" to describe the effect was for humor - probably a bad choice. Maybe red herring would have been better.
It shouldn't be a surprise to see your signal strength go from 5 down to 3 then later back up to 4 or even 5. This is just what radio waves do. On the other hand, if you are in a perfect setting, no hills, trees, buildings, powerlines, antennas of any sort for several miles, you might get a clean propagation where the signal falls off according to the rules.
I would never think linear, although I'd think inverse square.at a casual glance. Yes, I understand that obstacles and such matter. I had a somewhat related experience with standing sound waves when I was working in a semiconductor research lab, with very substantial wind flow and noise. There would be dead spots where it was almost silent, and loud spots where it was much louder than average.
And, yes, I also understand meter hysteresis. Control lags too, for that matter. The indicator doesn't just randomly bounce around. It goes from solid 5, to 5/4 bouncing, and then to 4/3 bouncing. I didn't find any of that surprising. I was reporting the observations, and looking to estimate how far I could go before it dropped to 3/2. At some point, I'll run the test.
Your post was a wee bit too condescending for my liking.
TCS
By "linear" I think he meant "in a line" rather than the mathematical concept of linear ... although my first reaction to the term is the same as yours.
What kind of semiconductor research did you do? I worked for a large semiconductor company for over 30 years, although I was in engineering and management.
And as just an anecdote about standing sound waves, I was drafted into the Army in 1970 and since I had an engineering degree I was sent to work as an engineering assistant at a place that did acceptance testing for new products the Army was thinking of buying. One such product was a small field deployable sound-proof and RF-proof conference room. Since it was a secret project, we were told to assemble it in a room that only happened to have only about four feet of clearance on all sides. As we took the various audio and RF measurements, it was obvious that standing waves for both were dominating the measurements, and where we placed the various sensors made huge differences in the readings. I told my civil service supervisor that all of the data was bogus, but he told us to just keep doing what were we doing anyway.
I worked at the TRW Microelectronics Center 100 years ago. You're a wee bit older than I am, but not a lot.
I started out as a tech in their lab. We made chips mostly for military spacecraft, processors, that kind of thing. For MilStar, we had to make chips that were able to survive a nuke going off not too far away.
As it evolved, my best skills were in running the lab and making the chips, not in the research per se. I was more proficient at running the ion implanter...a little particle beam weapon...than anybody else, including the engineers.
Just before I graduated college in economics and moved to the business/office staff, they had me developing metal evaporation techniques for new substrate materials. But I always missed running the lab.
Good times!
TCS
I worked at the TRW Microelectronics Center 100 years ago. You're a wee bit older than I am, but not a lot.
I started out as a tech in their lab. We made chips mostly for military spacecraft, processors, that kind of thing. For MilStar, we had to make chips that were able to survive a nuke going off not too far away.
As it evolved, my best skills were in running the lab and making the chips, not in the research per se. I was more proficient at running the ion implanter...a little particle beam weapon...than anybody else, including the engineers.
Just before I graduated college in economics and moved to the business/office staff, they had me developing metal evaporation techniques for new substrate materials. But I always missed running the lab.
Good times!
TCS
Cool. I remember that TRW made some terrific RF power transistors.
Take care!
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