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From 100% Signal Strength to DISCONNECTED?
953 17 2016-7-5
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MD_Icarus
Second Officer
United States
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I am puzzled about this event, and I need your inputs and help to undertand the cause:

I visited a friend who was so impressed with the P4 videos I was sending her, she purchased one too.

I showed her how to use Litchi and we flew a few missions wthout any glitches.

Then we flew a mission over water, about 0.2 miles from the shore line and a total distance from Home of about 1 mile. Even though we had direct line from the RC to the P4, and the distance was only about 1 mile, we experienced the dreaded Disconnected shown on the screen! She panicked and gave me the RC.

I could not see much, due to glare, other than the Disconnected!  
The story ends nicely though, I was able to stop the mission, and take control when the signal came back. I will let it continue next time and do nothing, since the Litchi mission is stored in the P4. But the time of disconnect was about 90 seconds, and the P4 was not that far away. I was afraid of a possible malfunction, frequency jammer... since w[size=14.5455px]e had flown over 2 miles over similar water terrain before.

I am curious about the reason we would go from 100% signal in one second, to Disconected the next?
Any ideas what may have caused it?


Some additional info, which may or may not be relevant:

Even though I leave the Transmission set to Auto, (I did not check it though before the mission) when I looked at the setting after the mission was complete, the channel was set to fixed 0.  Something is swithing from Auto to some arbitrary channel.  It is not me.  I will be checking this before each mission from now on.

This occured as the P4 was about 90 feet above and about 500 feet away from a small lighthouse. This lighthouse has a light beacon in it, which sends a light pulse out every 30 seconds. I am not sure if there is any radio signal as well, or a hidden cell tower inside, or even a drone-jammer,  and even though I called, they would not give me any details.


2016-7-5
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jstjohnz
lvl.2
Flight distance : 1146388 ft
United States
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Litchi has it's own channel setting, it will override what is selected in the GO app.  The channel selection is for the return video only though.   So the connection reestablished on it's own at some point?
2016-7-5
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Heebus
Second Officer

Canada
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I had a A diconnect 200 feet up and 1800 feet away, same thing from full strenght to disconnect in a second, but got it back in about 5 or 10 seconds, I'm flying over my home town so I just figured it was power line inteference or something of that nature. It is a scary moment, my comments prolly arent any help tho other then to let u kno ur not the only 1
2016-7-5
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Geebax
Captain
Australia
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'I am curious about the reason we would go from 100% signal in one second, to Disconected the next?
Any ideas what may have caused it? '


This is a phenomenum of digital radio communication called the 'Cliff Effect'. The signal is still OK up to a certain point, then it cannot be deciphered correctly any longer and just drops out, triggering a message about loss of signal. The Go App gives you a bars display that shows how strong the signal is, but as soon as it gets too weak, then it disconnects.

The term cliff effect refers to the fact the the signal appears to be OK up to a point, and then it acts like it fell off the edge of a cliff.
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MD_Icarus
Second Officer
United States
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jstjohnz Posted at 2016-7-5 18:29
Litchi has it's own channel setting, it will override what is selected in the GO app.  The channel s ...

I will make sure I set the litchi app to Auto before every mission then, and I hope it will stay in Auto. I just feel, that a single channel which may be good at the start, may not be as a good choice for the entire mission.
2016-7-5
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MD_Icarus
Second Officer
United States
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Heebus Posted at 2016-7-5 18:54
I had a A diconnect 200 feet up and 1800 feet away, same thing from full strenght to disconnect in a ...

Thanks for the reply!  It is strange since I was flying an area away from power lines.  The only structure was this small lighthouse. I will post a video later.

When the Disconnect lasts for almost 2 minutes, those were Very Very Long 2 Minutes!
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MD_Icarus
Second Officer
United States
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Geebax Posted at 2016-7-5 18:58
'I am curious about the reason we would go from 100% signal in one second, to Disconected the next?
...

I would expect to experience such when I have some obstruction between the P4 and the RC though.  There was nothing between them. The P4 in this case was only 1 mile away. I flew it about 2.5 miles previously in a different direction and the lowest signal was about mid 70's for a few seconds.
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Geebax
Captain
Australia
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MD_Icarus Posted at 2016-7-6 09:10
I would expect to experience such when I have some obstruction between the P4 and the RC though.   ...

It isn't always related to distance. It can be competing signals in the area as well.
2016-7-5
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egconstruger
lvl.3
Flight distance : 26906 ft
Dominican Republic
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Geebax Posted at 2016-7-5 18:58
'I am curious about the reason we would go from 100% signal in one second, to Disconected the next?
...

thanks for the explanation! Phantom 3 Standard owners are experiencing that after firmware 1.6.80 was installed, before the update the signal used to get low, or give you warnings in the app of interference, now at 20m height distance it just go to signal lost with full bars... and app goes black and white could it be firmware problems?.
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MD_Icarus
Second Officer
United States
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I am only guessing here, but I tend to go with:

1. I was flying using a single channel, instead of Auto Mode. I believe that in Auto Mode it keeps switching channels, so if one channel gets a high noise level, (interference, etc), it will switch to another channel, which may have better signal to noise ratio. But flying in a single channel is risky and I am going to make sure I never fly far using a single channel mode.

2. The lighthouse Red Green light beam may have caused it? It occurred at the 1 minute point of the video below, which is the start of the P4 facing the lighthouse.  It kept on it's litchi mission, but I took it home at about the 2 minute mark.

2a. There may be some radio transmitter or cell tower, but there is no such evidence and no history of such.

Ironically, I was able to make a video out of this mission anyway; some of it is Returning Home!
ttps://www.skypixel.com/videos/e4adc171-6fb8-4ec9-9856-55085cc8da50   


I am also hoping for some DJI feedback


2016-7-5
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Geebax
Captain
Australia
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egconstruger@gm Posted at 2016-7-6 10:56
thanks for the explanation! Phantom 3 Standard owners are experiencing that after firmware 1.6.80 w ...

I have no experience with the standard, so I cannot comment.
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Geebax
Captain
Australia
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MD_Icarus Posted at 2016-7-6 11:50
I am only guessing here, but I tend to go with:

1. I was flying using a single channel, instead of  ...

With regard to:

1. Single channel mode. It is best to leave it in auto mode, as that is the way it is meant to work.
2. The Lighthouse really is an extremely unlikey culprit. I would rule it out.
2a. There are a thousand and one devices that use the same frequency allocation as the Phantoms, so it could be anything causing interferrence. Cell towers are almost certainly not a problem, I have flown right up to a huge array of them and it made no difference at all.
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tomkes
lvl.2

Switzerland
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I have a similar issue. While flying over a lake or flying from a hill directly to the valley and always in both cases there is nothing between RC and the P4, the singal is lost from one second to another when the P4 is approx. 1400 top 1500 meters away, sometimes earlier.   

I am still wondering how people are able to  have a stable signal for some kilometers.

A bit disappointing as DJi pronounced on their website that the P4 should cover a range of about 3.5 km.

The weak transmission signal Problem has not been completely fixed.
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MD_Icarus
Second Officer
United States
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This experience put the breaks on some upcoming 3  mile out flight plans!

I am going to start slow again, do some test flights with both P4s and keep a close eye on the transmission channel setting in Litchi before every flight.

Maybe this experience was helpful, to make me more cautious and keep a closer eye on the settings.
Even though my friend had the antenna booster, I do not believe they really work; I actually think they may actually degrade the beam width.
Anyone had some proven results using them?
2016-7-6
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Heebus
Second Officer

Canada
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I have read several people saying the same thing, that the boosters dont work, infact they make it worse, I beleive you can find a few threads on here that people have said as much... just a thought tho (prolly null n mute) no way the 2 P4's coulda temp conflicted with each others signal?, prolly not but just a thought
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Geebax
Captain
Australia
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tomkes Posted at 2016-7-6 17:16
I have a similar issue. While flying over a lake or flying from a hill directly to the valley and al ...


'A bit disappointing as DJi pronounced on their website that the P4 should cover a range of about 3.5 km. '


And there will be many who are achieving that sort of distance, in fact a number of P4 owners have reported here that they are getting very long distances.

It is not under the control of DJI, they publish figures that can be achieved under good conditions, but they have no control over where you fly.

Iif you are flying in an urban environment, then you most certainly will not get long range, the community you are flying over is chock full of computer with WiFi systems, all competing with your Phantom for radio access.
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MD_Icarus
Second Officer
United States
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Heebus Posted at 2016-7-6 17:49
I have read several people saying the same thing, that the boosters dont work, infact they make it w ...

I was only using one P4 at the time.

The little bit I know about antennas and using these cones to increase gain or directivity is that they work at much higher frequencies than the 2.4 GHZ used; it is also a linear type (not a circular type) , and they have to be directed precisely at the target.  If one imagines the number 8 then what they do at higher frequencies is elongate one side of the 8 (make it thinner and longer) and reduce the back side)
The number 8 represents the covered area.
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Heebus
Second Officer

Canada
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ok, I think I understand... n wasnt sure about 1 or 2 P4
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