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Can flying near radio towers interfere with Mavic Pro?

adam3112

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Hi all,

Just before I explain, I just want to say that I replaced my faulty equipment mentioned in the other thread and got myself a brand new, sealed Mavic 1 Pro. My Mavic's IMU and Compass is calibrated and showing as normal in the settings. In fact everything is showing as normal. I had calibrated them yesterday when I took it out on a previous flight.

So today being my second flight, I took my Mavic up to a viewpoint which happens to be near a radio tower. I was about 200 Meters away from the tower but for some reason as soon as I took off and went forward (with 13 Satellites), I suddenly got Compass error and my Mavic was put in to atti mode, flung forward with the strong wind and missed the trees by Inches. I'm still amazed at how it missed. Watching it back on the video still makes my heart sink, these trees were easily 70-80 ft high and the drone was being pushed fast. I'll try and post a video of it.

So after this near nightmare, I came to a stop at the other side of the tree line in an open area, almost having a heart attack. I then got weak GPS signal. A few seconds later, GPS connectivity got restored with 18 satellites. I flew back and landed at the home point straight away.

I took off a second time and I got a message pop up on the app saying 'Strong Wireless Interference. Fly with caution.' Luckily it stayed in GPS mode for the duration of the flight and I got it back safely.

So my question is, is it likely the radio tower interfered with my Mavic today? I'm hoping there isn't an underlying problem.

Thanks.
 

adam3112

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Here's the video of the near crash. You can see the Radio Tower in the background at the start.
 

FoxhallGH

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There's a good chance that the radio tower has directional antennas that are firing focused beams of radio frequency [RF] energy to cover regional areas or to link to other radio towers that pass the service on. The frequencies of these radio beams are probably quite different to that being used to control your drone from your RC controller - BUT - there are several things that can be happening that will cause the kind of problems you have experienced;
- Because the RF energy is focused by the high-gain [directional] antennas on the mast, your drone will be 'swamped' with RF energy if it flies into or near one of these beams.
- Because of the nature of the 'scatter' off the directional antennas, you usually get low powered side-lobes that are just as powerful at 50 metres, as the main beam is at 5 Km (therefore this is not just about being in front of the antenna!).
- RF energy is classic Electro-Magnetic radiation, and therefore, it induces electrical current in anything that can conduct electricity.
- Your drone is full of batteries, wires and electrical components that are there to conduct electrical energy & signals.
Another way of looking at this, is it's like you and me trying to have a conversation in front of a stage speaker at a Guns and Roses concert!
Bottom line is that even if the Radio mast is broadcasting on a different frequency than that of your RC controller - It's highly likely to be 'Phasers on Stun!' to your drone, as it will have a whole lot of RF noise & interference blasting into it that will fight with the signals that are trying to keep it in control.
From your experience - 'Strong Wireless Interference' - is probably an accurate description, and it appears, its a warning that should be taken seriously.
 

adam3112

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There's a good chance that the radio tower has directional antennas that are firing focused beams of radio frequency [RF] energy to cover regional areas or to link to other radio towers that pass the service on. The frequencies of these radio beams are probably quite different to that being used to control your drone from your RC controller - BUT - there are several things that can be happening that will cause the kind of problems you have experienced;
- Because the RF energy is focused by the high-gain [directional] antennas on the mast, your drone will be 'swamped' with RF energy if it flies into or near one of these beams.
- Because of the nature of the 'scatter' off the directional antennas, you usually get low powered side-lobes that are just as powerful at 50 metres, as the main beam is at 5 Km (therefore this is not just about being in front of the antenna!).
- RF energy is classic Electro-Magnetic radiation, and therefore, it induces electrical current in anything that can conduct electricity.
- Your drone is full of batteries, wires and electrical components that are there to conduct electrical energy & signals.
Another way of looking at this, is it's like you and me trying to have a conversation in front of a stage speaker at a Guns and Roses concert!
Bottom line is that even if the Radio mast is broadcasting on a different frequency than that of your RC controller - It's highly likely to be 'Phasers on Stun!' to your drone, as it will have a whole lot of RF noise & interference blasting into it that will fight with the signals that are trying to keep it in control.
From your experience - 'Strong Wireless Interference' - is probably an accurate description, and it appears, its a warning that should be taken seriously.
Thanks FoxhallGH. I think this is a big lesson learnt. Will probably avoid this area and places like it in the future.
 

Meta4

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So today being my second flight, I took my Mavic up to a viewpoint which happens to be near a radio tower. I was about 200 Meters away from the tower but for some reason as soon as I took off and went forward (with 13 Satellites), I suddenly got Compass error and my Mavic was put in to atti mode, flung forward with the strong wind and missed the trees by Inches. I'm still amazed at how it missed. Watching it back on the video still makes my heart sink, these trees were easily 70-80 ft high and the drone was being pushed fast. I'll try and post a video of it.
I took off a second time and I got a message pop up on the app saying 'Strong Wireless Interference. Fly with caution.' Luckily it stayed in GPS mode for the duration of the flight and I got it back safely.
So my question is, is it likely the radio tower interfered with my Mavic today? I'm hoping there isn't an underlying problem.
At 200 metres, the radio tower had absolutely no effect on your compass.
Not any, zero, zip, zilch, none at all.
Your launch spot probably is to blame.
As you described the incident, it sounds exactly like what can happen when you launch from a steel or reinforced concrete surface which can interfere with the compass.

I took off a second time and I got a message pop up on the app saying 'Strong Wireless Interference. Fly with caution.' Luckily it stayed in GPS mode for the duration of the flight and I got it back safely.
Wireless interference could come from almost anywhere, home wifi is a common cause.
It may or may not have had anything to do with the tower.
 

adam3112

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At 200 metres, the radio tower had absolutely no effect on your compass.
Not any, zero, zip, zilch, none at all.
Your launch spot probably is to blame.
As you described the incident, it sounds exactly like what can happen when you launch from a steel or reinforced concrete surface which can interfere with the compass.


Wireless interference could come from almost anywhere, home wifi is a common cause.
It may or may not have had anything to do with the tower.
Except I launched it from a grassy gravel pathway. Unless there is something underneith the ground which caused it?

Also, there were no houses nearby as I was surrounded by fields and farmland.

Sorry if the video feed posted above isn’t working, but it shows the environment I was in quite well in there.
 

Meta4

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Except I launched it from a grassy gravel pathway. Unless there is something underneith the ground which caused it?
Also, there were no houses nearby as I was surrounded by fields and farmland.
Sorry if the video feed posted above isn’t working, but it shows the environment I was in quite well in there.
The air is full of radio traffic. You can experience wireless interference almost anywhere.

Your first incident definitely was not related to a tower 200 metres away.
Video isn't much help analysing flight incidents.
To look further into the incident, you would need to posy flight data.
Go to DJI Flight Log Viewer - Phantom Help
Follow the instructions there to upload your flight record from your phone or tablet.
Come back and post a link to the report it gives you.
 

SpinItUp

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If the tower is between you and the craft would be more likely but that shows you (& controller) in front when taking off and as soon as you got any distance I think the masts did have an influence, I'd be surprised if they didn't!
Edit; looks like aTV tower plus other services that can be using it and other masts dotted around nearby.
Is that Clee Hill on the horizon when you turn it around?
 
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adam3112

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If the tower is between you and the craft would be more likely but that shows you (& controller) in front when taking off and as soon as you got any distance I think the masts did have an influence, I'd be surprised if they didn't!
Edit; looks like aTV tower plus other services that can be using it and other masts dotted around nearby.
Is that Clee Hill on the horizon when you turn it around?
When I turned around it would have been facing south towards Gatwick and maybe abit of Horsham as I was on top of Reigate Hill (UK)
 
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Meta4

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When I turned around it would have been facing south towards Gatwick and maybe abit of Horsham as I was on top of Reigate Hill (UK)
At worst, all the tower could affect you would be a little radio interference.
Radio signals don't have any effect on your compass and that's the problem you described.
Forget the tower, it was not the problem.
Post flight data if you are interested to know what really happened.
 

adam3112

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At worst, all the tower could affect you would be a little radio interference.
Radio signals don't have any effect on your compass and that's the problem you described.
Forget the tower, it was not the problem.
Post flight data if you are interested to know what really happened.
I’ll post it abit later today. I know it’s easy to put these things down to pilot error but as far as I’m concerned, I did everything correctly when I was flying it and losing gps was completely outside of my control.
 

Meta4

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I’ll post it abit later today. I know it’s easy to put these things down to pilot error but as far as I’m concerned, I did everything correctly when I was flying it and losing gps was completely outside of my control.
No-one has suggested pilot error. .. Just that the tower was not the problem.
 

SpinItUp

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I was on top of Reigate Hill (UK)
That Fort under the ground is full of Iron bars

+
Radio City on Reigate Hill
It's known that during the Second World War, there were many radio aerials around Reigate Hill and the area’s nick-name was Radio City. Local residents who knew ARP wardens during the war believed that the structures on and around Reigate Hill were listening posts.
Further evidence to support the theory
Armed with this information, and having taken a look at similar structures in the area, the team have since found two electrical insulators and cabling close to the structures which they now believe to be evidence of the structures being linked to radio communications.


I think that's the answer!
Reigate Fort



Edit; Great place for a TV transmitter if you live around Reigate and want to know your channel muxes;)

Industrial_structures.jpg May also have played a part
 
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adam3112

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That Fort under the ground is full of Iron bars

+
Radio City on Reigate Hill
It's known that during the Second World War, there were many radio aerials around Reigate Hill and the area’s nick-name was Radio City. Local residents who knew ARP wardens during the war believed that the structures on and around Reigate Hill were listening posts.
Further evidence to support the theory
Armed with this information, and having taken a look at similar structures in the area, the team have since found two electrical insulators and cabling close to the structures which they now believe to be evidence of the structures being linked to radio communications.


I think that's the answer!
Reigate Fort



Edit; Great place for a TV transmitter if you live around Reigate and want to know your channel muxes;)

View attachment 52291 May also have played a part
Thanks Spinitup, the fort and surrounding areas would explain alot actually especially if there’s alot of metal underground in that spot. I maybe should have taken it to the actual viewpoint, further away from the fort and the tower. The outcome may have been different.

I’m quite busy today so I havent got time to sort the flight data right now but should have it up this-evening. Thumbswayup
 
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ac0j

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Thanks Spinitup, the fort and surrounding areas would explain alot actually especially if there’s alot of metal underground in that spot. I maybe should have taken it to the actual viewpoint, further away from the fort and the tower. The outcome may have been different.

I’m quite busy today so I havent got time to sort the flight data right now but should have it up this-evening. Thumbswayup
If that WAS a radio listening area. There is a huge possibility that long metal radials were buried projecting out from the tower base. They added those for HF radio to create a good ground plane for the antenna.

I live a few miles from an old FCC monitoring station. In hall county Nebraska. It has several acres of antenna farms. There is still some crazy looking things out there! I think it is out of commission, but the gate is still secured and there is often a vehicle or two there. It can be found on google earth, but most of the antenna arrays are gone now.
 

FoxhallGH

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Here's another link to my video:

IMG_8678.TRIM - Streamable
Looking at this footage, you can see a pair of white drum-like enclosures about half way up the tower, pointing in your direction. These are highly directional parabolic [dish] antennas. To give you some idea of the gain that antenna's like this have, the Voyager space probe is still in touch with JPL from past the edge of our Solar System, using only a 23 Watt S-Band radio - thanks to a 3-metre Parabolic dish antenna!
 

ac0j

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Looking at this footage, you can see a pair of white drum-like enclosures about half way up the tower, pointing in your direction. These are highly directional parabolic [dish] antennas. To give you some idea of the gain that antenna's like this have, the Voyager space probe is still in touch with JPL from past the edge of our Solar System, using only a 23 Watt S-Band radio - thanks to a 3-metre Parabolic dish antenna!
Its all about the antennas at those low powers. And receiver sensitivity. Still wouldnt effect a compass.
 

FoxhallGH

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Yes - As long as the compass in the Mavic Pro doesn't use electricity and electronic components! [hmmmm] ... Receiver sensitivity has nothing to do with this because it's nothing to do with the RC receiver getting signals it can't understand ... It's actually to do with something called 'induced EMF' (ElectroMotive Force). Its the same principle as why an air-burst atomic bomb can fry ALL electronics under it - not just your radio receiver. Radio waves are EMF energy, and are capable of inducing electrical currents in 'conductive' materials. All of the electronics on your Drone - including the compass - are susceptible to induced EMF. The induced currents are complex in that they are happening at the rate of the external transmitter, and also reflect any frequency and/or amplitude modulation applied to the carrier. I used to work on a Marconi Surveillance Radar system used by the CAA (I was trained as a telecommunications Engineer by the CAA) - People who lived in the same City were always asking me what the 'buzz' was they heard at regular intervals when they played their CD's ... Every 7 seconds as the Radar antenna rotated past them, their CD player would get a burst of 400Hz modulated RF energy ... Same thing ... Induced electrical current .
The big clue here is that Adam3112's controller gave him a message "Strong Wireless Interference. Fly with caution." The Mavic knew it wasn't nice out there ...
 
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