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Downlink Lost

Zonian

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So a scary event (for me) today. It was a relatively nice day in Chicagoland so I decided to just do a little flying in my yard...nothing fancy or far out or high because it was a also little windy...

Anyway, the MP1 was about 8 minutes into an uneventful flight, about 9 ft away from me, and about 2 ft off the ground...all of a sudden I get this "downlink lost" message, and I have no control from either stick inputs. The MP1 didn't go anywhere, it just hovered there for about 45 seconds...it was rock solid in space, but I HAD NO CONTROL. I could have walked over to it and grabbed it, which I was ready to do but then it re- connected and went straight into autolanding mode.

Anyone have any ideas of what causes this? It has never happened to me, so now. yeah, I'm kinda nervous.
 

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boblui

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The drone was just next to you. There must be something seriously wrong with it. I am afraid sending it back to DJI is the only way to go.
 

slup

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Have seen it once here at the forum ... so check off so neither of the 2 antenna cables are broken due to folding/unfolding & turning the antennas. Even with one of the cables totally off a AC-RC connection can be made but it's really laggy.

1614774848235.png
 

eaglesurfing

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Make you wonder what is under the ground right there.
 

Zonian

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Poor pointing of directional antenna?

I was thinking maybe this as well. I was sitting on my front porch steps, looking straight ahead (as was the RC). The bird was off to my right at about a 45 degree angle. Maybe TOO CLOSE ??

But when I lost downlink, the first thing I did in reaction was to turn the RC right to the bird, (antennas were straight up as per the manual) I probably did this within the first 5 seconds of getting the notice... nothing happened.

Could random interference be the cause?
I suppose that is possible. I tried for 15 minutes to "recreate" the event on a subsequent flight, but I couldn't. I even pointed the antennas 90 degrees off to the side...no clue.
The drone was just next to you. There must be something seriously wrong with it. I am afraid sending it back to DJI is the only way to go.

Don't think I want to do that...yet.

Do you know if there would there be further info on a file in the bird that might explain this?
 

Zonian

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Have seen it once here at the forum ... so check off so neither of the 2 antenna cables are broken due to folding/unfolding & turning the antennas. Even with one of the cables totally off a AC-RC connection can be made but it's really laggy.

View attachment 124990


I will check
 

Zonian

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Have seen it once here at the forum ... so check off so neither of the 2 antenna cables are broken due to folding/unfolding & turning the antennas. Even with one of the cables totally off a AC-RC connection can be made but it's really laggy.

View attachment 124990


OK, so I checked and there doesn't appear to be any issue with the antenna cables.
 

boblui

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Don't think I want to do that...yet.

Do you know if there would there be further info on a file in the bird that might explain this?
I believe so but I am afraid only DJI is able to read the data. The flight log files in the phone can be analysed by some of us but they contain too little info on the radio connection to provide any meaningful insights.
 

Zonian

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I believe so but I am afraid only DJI is able to read the data. The flight log files in the phone can be analysed by some of us but they contain too little info on the radio connection to provide any meaningful insights.
Roger that. Just for purposes of elimination, this would almost certainly be an issue between the Mavic and the controller, correct?? Nothing to do with my smartphone or phone connection, correct?
 

boblui

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Roger that. Just for purposes of elimination, this would almost certainly be an issue between the Mavic and the controller, correct?? Nothing to do with my smartphone or phone connection, correct?
I am pretty sure about that because the phone or phone connection should not cause the drone to be unresponsive to stick inputs. As a matter of fact, you can fly the drone with the controller only if everythings are working OK.
 
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Zonian

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I am pretty sure about that because the phone or phone connection should not cause the drone to be unresponsive to stick inputs. As a matter of fact, you can fly the drone with the controller only if everythings are working OK.

My thoughts exactly. Thank you.


Could random interference be the cause?
Make you wonder what is under the ground right there.

OK. So I've been trying to scour the interwebs for everything related to "downlink lost", and it seems almost everything I find points to some kind of interference as the likely culprit.

Coincindentally, my house has a smart water meter located in the basement, probably within about 10 ft from both where I was sitting and where the mavic was. I don't know exactly how it works, how often, or on what frequency, but it is my understanding that somehow it transmits water usage data.

Anyone know what the frequency is for the RC-Mavic connection?
 

Dave Maine

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Downlink lost will not impact stick control. It is used mostly for video download. Control inputs to the drone use the uplink path.
 

Zonian

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Downlink lost will not impact stick control. It is used mostly for video download. Control inputs to the drone use the uplink path.

Hmmn. I did not get any message about "uplink"...but I definitely lost ALL stick control.
 

Dave Maine

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Not questioning your observation, but suggesting guidance on the investigation path.
 

Zonian

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Not questioning your observation, but suggesting guidance on the investigation path.

Understood...no problem.

Since the bird just hovered there when downlink was lost, I did not notice any movement on the screen image.

I will check the sd card to see if I was by chance recording at that time...I do not remember.
 

Dave Maine

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What was your return to home setting set to? If you loose uplink connection for more than a couple of seconds, the drone will switch automatically into RTH mode, and will do whatever is set in that setting. If it is set to hover, it will just sit there. If it is set to return home, it will return home and land.

If it is close to home, it will land in place, using the downward sensors to determine if the landing site below it is usable. If so, it will land, if not, it will descend to a couple of feet from the ground and just hover.
 

Zonian

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Ok, I was not recording at the time. However not sure that is relevant since the SD card is local on the bird, uplink or downlink issues either way should not affect the video on the card, but only the video feed on my screen...and honestly I just don't remember what happened with that because I was so preoccupied and freaked out about not having any stick control.

I'm thinking more and more about the smart water meter mentioned in post #13 as the culprit; but I cannot find anywhere what frequency it transmits on. In 3.5 years my RC-Mavic connection has been rock solid...this is the only incidence and I cannot think of anything else that would cause this issue.
 

Dave Maine

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Depending on the DJI model and settings, it will auto select a channel either in the 2 MHz range or 5 MHz range, and while in flight switch channels as the WiFi signal strength changes in flight.
 
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