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Sudden Loss of Satellite Signal

WanderLost

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I was flying my Mavic 3E about 2000 feet away at around 325 feet around some new construction sites. There were no obstructions between me and the drone and twice when I was at a particular angle to the metal buildings, I got a "controller signal blocked" which resolved as soon as I moved. I could still see where the drone was in the sky.

Then I got a "collision warning" even though there was nothing at my altitude - not even birds - and the number of satellites dropped to zero. After moving again, the satellites picked right back up.

I brought the drone back to inspect it and saw nothing wrong so I'm assuming some kind of RFI. I flew back to the spot again and was able to repeat the issue. One possible issue is a cell/antenna tower about 500 feet away - but I've flown much closer and all around this tower in the past without issue. However, the factory I was over does a lot of welding - perhaps that might be an issue? In the 2nd flight, I tried flying through the area again and then flew past it to see if I ran into range issues which didn't appear to be a problem.

Is it possible I flew into the path of a microwave beam from the tower and that affected the drone signals?

Flight log #1 here: DJI Flight Log Viewer - PhantomHelp.com
Flight log #2 here: DJI Flight Log Viewer - PhantomHelp.com
 
Logs play for me.Thumbswayup
The satellite count went to zero, wow. Yes in a pole building or under ground. :rolleyes:

Second, strong controller signal interference tower related, beyond me.

In the states there is a FCC data file you add to google earth pro.

You can see the frequencies, the direction of those dish antennas, etc.

Also see location of cell towers, Lat, Lon, Elevation and I think the height of the tower.

Its all I got
Waiting for the real guys now.

Rod .
 
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hi,

It seems that there were 2 issues. (1) drop in radio signal and (2) RFI for GPS.

For (1) , the most likely cause is due to the blocking of radio line of sight. Assuming you were around the take off point with the RC controller during the flight, the nearby building/ tree would cause blocking of radio signal. With this low angle in horizon, it may happen that you can see the drone but your RC rontroller "can't". Here is the view generated in Google Earth. I think it can well explain the problem.

1732776356363.png

For (2), GPS drop happened seperately. we can rule out the following:
  • GPS level remained normal during most of the flight so hardware problem is unlikely.
  • Cell tower (for mobile network) unlikely to cause interference.
  • Solar weather report from NOAA for 27 Nov was "None (below G1)".

After ruling out the non-factor, the other possible cause:
  • Interference from energy equipment by "EnerQuest Technology Solutions Inc.", which is located near the flight area. Electromagnetic interference might be generated during switch on/off certain high voltage equipment. That would explain why previous flight were not affected and the relative short period of interference.
  • Unintentional GPS jamming: illegal but not difficult/impossible.... I've heard that some truck drive would have such jammer to mask their exact location to the employer.
  • CIA cover base nearby.... that can explain everything.....
Anyway, able to fly the drone back without GPS (even during short period of time) was impressive and may be lucky~
 
hi,

It seems that there were 2 issues. (1) drop in radio signal and (2) RFI for GPS.

For (1) , the most likely cause is due to the blocking of radio line of sight. Assuming you were around the take off point with the RC controller during the flight, the nearby building/ tree would cause blocking of radio signal. With this low angle in horizon, it may happen that you can see the drone but your RC rontroller "can't". Here is the view generated in Google Earth. I think it can well explain the problem.

View attachment 179379

For (2), GPS drop happened seperately. we can rule out the following:
  • GPS level remained normal during most of the flight so hardware problem is unlikely.
  • Cell tower (for mobile network) unlikely to cause interference.
  • Solar weather report from NOAA for 27 Nov was "None (below G1)".

After ruling out the non-factor, the other possible cause:
  • Interference from energy equipment by "EnerQuest Technology Solutions Inc.", which is located near the flight area. Electromagnetic interference might be generated during switch on/off certain high voltage equipment. That would explain why previous flight were not affected and the relative short period of interference.
  • Unintentional GPS jamming: illegal but not difficult/impossible.... I've heard that some truck drive would have such jammer to mask their exact location to the employer.
  • CIA cover base nearby.... that can explain everything.....
Anyway, able to fly the drone back without GPS (even during short period of time) was impressive and may be lucky~
Thanks for your detailed analysis - very impressive! I'll start with the easy stuff - CIA - unlikely since I'm in Canada - but we do have CSIS here - a kind of younger brother to the CIA.
Enerquest makes control equipment for wind and solar farm installations - definitely a possibility. The yellow and blue buildings where I was hovering near is Refac - a metal fabricating factory - lots of welding going on. Plasma and arc welding produce pretty nasty RFI I think so that could also be an issue.

It's interesting you mention that my signal might be line of sight blocked. I've flown in this area many times for roof inspections and flooding monitoring and I definitely run into this issue when I'm below 150 feet. I've usually been quite safe at the 300 foot altitude I was at, but perhaps there were enough metal buildings to cause some multipath distortion and loss of signal.

I should try again but find a closer spot to eliminate that issue.

The cell tower also has microwave and broadband internet antennas on it.

Your Google view is excellent and I would have definitely been blocked to some extent if I was standing where the view is. I was about 50 feet to the north (left in the picture) so as to avoid the grey house from blocking the view to the controller and aircraft.

I never heard of GPS spoofing/blocking equipment for truckers. Very interesting. There are a lot of trucks around at these places - especially right now when Enerquest is gearing up for a big shipment. There were at least 5 huge semi's and a big crane onsite to pack up the latest installation build.

I was intrigued that my issue was confined to a small spot in the sky. I'd like to explore it more, but I'm kind of spooked. I suppose if I lost all connection the drone "might" RTH, but if it doesn't have GPS, then it'll just hover and then land on the spot right?
 
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If you lose GPS + control signal, your drone won't waste any time hovering.
It will go straight to autolanding.
Ah - good to know. If I do test this, I better make sure I have a suitable landing spot beneath me!
 
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If you lose GPS + control signal, your drone won't waste any time hovering.
It will go straight to autolanding.
Apparently, the manual says it will hover for a time and then land. I don't know what the length of time would be - a set amount - or a percentage of remaining battery life.
RTHSignal Loss.jpg
 
If in the same area again, can you walk to a closer / different position and still see the drone on the area of odd behaviour?
If so I’d be tempted to set loss of signal behaviour to hover rather than RTH, then get closer to re establish connection
 
Apparently, the manual says it will hover for a time and then land. I don't know what the length of time would be - a set amount - or a percentage of remaining battery life.
I've had this happen recently and if there was any hovering, it wasn't long enough to notice .. a couple of seconds at most.
 
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If in the same area again, can you walk to a closer / different position and still see the drone on the area of odd behaviour?
If so I’d be tempted to set loss of signal behaviour to hover rather than RTH, then get closer to re establish connection
That was my thought. If I was close (like right underneath it) I might be able to see if I can position it so the GPS is blocked and figure out how/where it's happening.
 
If you lose GPS + control signal, your drone won't waste any time hovering.
It will go straight to autolanding.
It would first hover. Wind will take it everywhere. It would just like flying the drone with hands-off in atti mode. Height and heading would be by large maintained (control by barometer and electronic compass).

It would start landing when the batteries are about to dry.

I suppose the logic is that auto landing without control is risky so it would remain hover for as long as it takes, until either one system restores. It would only land when such options become impossible (i.e. when battery are out) so it will auto-land.

I also suppose DJI (or any drone manufacturer) can change the operation logic in their drone but I don't see any reason why they would do it. But I have to admit that such possibility exist and I have not tried this on every drone.


Edited notes: the above was found to be incorrect.
 
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Thanks for your detailed analysis - very impressive! I'll start with the easy stuff - CIA - unlikely since I'm in Canada - but we do have CSIS here - a kind of younger brother to the CIA.

The cell tower also has microwave and broadband internet antennas on it.

I never heard of GPS spoofing/blocking equipment for truckers. Very interesting. There are a lot of trucks around at these places - especially right now when Enerquest is gearing up for a big shipment. There were at least 5 huge semi's and a big crane onsite to pack up the latest installation build.

I was intrigued that my issue was confined to a small spot in the sky. I'd like to explore it more, but I'm kind of spooked. I suppose if I lost all connection the drone "might" RTH, but if it doesn't have GPS, then it'll just hover and then land on the spot right?

About CIA/CSIS.... pls excuse my poor sence of humor..... just joking.

I am not sure if microwave would cause interference. I can tell that mobile phone network (2,3,4,5G) won't have effect on DJI drone. And I am not very clear what "broadband internet antennas" you are referring to. If that is a gaint 2.4GHz/ 5.8GHz source, then yes, it would definately cause interference.

Some years ago, I tried search "truck" and "GPS" in amazon and this kind of products just jump up, pages after pages. I suppose this was popular but that wasn't allowed to export so I never tried it in person. Haven't follow up on that afterward. May be the control is more stringent now.

For GPS issue, it is more likely to be a wide spread issue than a specific location issue. Think about this, the GPS sat is about 20,000 km away from earth surface (some satellite of BeiDou is closer but still a few thousand km away at least) so the signal are acatually weak. Ground interference (with the right frequency) are very very likely to be much stronger than that. So, it is likely to affect a larger area (at least a few sq km).

That's why I speculate the interference was unintentional (given its short period of time). And it seems that you were just flying over that area during the bad timing (you were flying in your east all along). I guess, if you fly towards your north or west side, you may still experience something similiar, may be just not as significant.
 
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It would first hover. Wind will take it everywhere. It would just like flying the drone with hands-off in atti mode. Height and heading would be by large maintained (control by barometer and electronic compass).
That's what would happen if GPS alone was lost.
It would start landing when the batteries are about to dry.
This is not what the manual states or what happened to my drone last week.
 
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If that factory does arc welding, i is entirely possible that your drone got hit with a LOT of RF interference. Gas welding wouldn't be a problem, but arc welding puts out broad spectrum electrical noise of very high intensity. I'm not saying that's the problem, but it very well could be. Arc welders are almost an ideal close proximity jammer. You can check this by taking almost any radio there and see what the result is.

Keep in min that people used to communicate thousands of miles with spark transmitters.
 
This thread has me interested. There is a location I had to film for a commercial gig and there was a VERY specific area where the drone claimed no satellites fixed, but upon exiting it they came right back. I have been meaning to go back there someday soon and see what my phone does in the same area.
 
This thread has me interested. There is a location I had to film for a commercial gig and there was a VERY specific area where the drone claimed no satellites fixed, but upon exiting it they came right back. I have been meaning to go back there someday soon and see what my phone does in the same area.
Very interested in what you find. When it happened to me, it was almost like my drone was hit with an EMP causing several warnings to popup. The weirdest one was "collision" when nothing actually hit it. If the RF interference messed with the IMUs electronic mind, perhaps that could explain the warning.
 
Usually RF interference is only going to disrupt your control and vision signal.
Yes - that's been my experience over the time I've been flying, but I was looking for some way to explain the "collision" warning that popped up for a second.
 

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