Signal a problem?

[Karl2951]

Taking vlos put of the equation, can you fly the otherside of hills, buildings and trees without signal loss? Or will the mavic just RTH?

 

[Gary cato]

No you cant and yes it will (sometimes)

Do not fly below and behind hills, buildings are any other thing you are not standing on the edge off or in direct line with and above it.

As for RTH you take your chances, it should RTH and for me it always has done so perfectly but i also have not flown behind or dropped down below anything. Others have and some never saw the Mavic again for various reasons.

simple answer is no dont do it.

 

[hychewright]

Karl, I agree with Gary don't do it. You don't won't to lose your Mavic.

 

[Kestrel]

I don't agree with the statement that you can't fly behind things, contrary to what is commonly believed, I've actually took off and flew past hills, buildings and other obstructions without losing signal, lost bars yes but I have yet to full on lose signal with my Mavic. And I wasn't that high. Do I recommend it? no.

 

[Gary cato]

I don't agree with the statement that you can't fly behind things, contrary to what is commonly believed, I've actually took off and flew past hills, buildings and other obstructions without losing signal, lost bars yes but I have yet to full on lose signal with my Mavic. And I wasn't that high. Do I recommend it? no.

i did not say you cant fly behind things i said behind and below. If the Op wants to take a chance that's fine. Not my Mavic lol.

 

[Michael Ainsworth]

So what would likely happen if I flew through a short 5 metre tunnel? By the time I lost signal it would be out the other side hopefully picking up signal again?
Or is this likely to crash and burn.

 

[Gary cato]

So what would likely happen if I flew through a short 5 metre tunnel? By the time I lost signal it would be out the other side hopefully picking up signal again?
Or is this likely to crash and burn.

No Idea but been thinking about this myself, if signal loss is instant you will be in atti mode fast the if all gps fails it will attempt to RTH. Not good in a tunnel me thinks

 

[Michael Ainsworth]

Yeah, I've got an idea to run up a stream that goes under a footpath then into a small lake. Would look really cool but I can't justify gambling the Drone on this.

 

[Gary cato]

Yeah, I've got an idea to run up a stream that goes under a footpath then into a small lake. Would look really cool but I can't justify gambling the Drone on this.

Prog guards and floats mmmmmmj

 

[Kestrel]

i did not say you cant fly behind things i said behind and below. If the Op wants to take a chance that's fine. Not my Mavic lol.

Still the original Question can you fly behind hills and buildings without signal loss, its a resounding yes you can.

 

[Gary cato]

Still the original Question can you fly behind hills and buildings without signal loss, its a resounding yes you can.

Ok yes you can, all opinions are valid, good luck to the Op with that. Hope he does not come back later looking for Msinger etc..

i think we are talking two different scenarios here.

 

[Kilrah]

Unless it's very close to you you WILL lose signal when flying behind a solid obstacle.
What happens next depends on your configuration (failsafe action, RTH height...) that you need to check VERY thoroughly if you're going to do that, many haven't, and... crashed/lost their aircraft.

 

[Gary cato]

If you fly over a building or hill and keep going eventually you will be behind it unless you want to raise your height. the further you move over the building or hill. the closer you are to a tall building when you fly over it the quicker the building or hill will obscure your Mavic from controller.

Try standing very close to a tall building lets say 200 feet away, fly over it and keep going at that height and see how fast you lose signal, Do the same from 500m away and the Mavic RC will still be giving out more signal to the Mavic.

So the closer you stand to a bulding and fly over it the faster you will lose the Mavic

 

[SkunkWerx's]

I don't agree with the statement that you can't fly behind things, contrary to what is commonly believed, I've actually took off and flew past hills, buildings and other obstructions without losing signal, lost bars yes but I have yet to full on lose signal with my Mavic. And I wasn't that high. Do I recommend it? no.

It is possible because your signals are bouncing off your surrounding's examples flag poles , fencing metal frame windows cars mainly anything metal like aluminum siding even water on the grass basically the signals are being reflected back and fourth from the RC to the AC and vice versa

 

[WEOTN]

DLOS can be a good thing too! I'd use waypoints if I knew I'd be obstructed from DLOS of the drone, but that's not allowed in the USA, though I bought Litchi for that purpose. They used to teach HD Thoreau and Civil Disobedience in my school back in the 60's, it wasn't lost on me. I was a boyscout too, and Be Prepared wasn't lost on me either. I like options. Having been a HAM radio operator gives me great respect for the problems that can arise, and I'm just not willing to gamble a grand on a lark. You gotta weigh potential winnings vs losses and choose for yourself.

 

[SkunkWerx's]

DLOS can be a good thing too! I'd use waypoints if I knew I'd be obstructed from DLOS of the drone, but that's not allowed in the USA, though I bought Litchi for that purpose. They used to teach HD Thoreau and Civil Disobedience in my school back in the 60's, it wasn't lost on me. I was a boyscout too, and Be Prepared wasn't lost on me either. I like options. Having been a HAM radio operator gives me great respect for the problems that can arise, and I'm just not willing to gamble a grand on a lark. You gotta weigh potential winnings vs losses and choose for yourself.

There's nothing wrong with what you were / did when you were growing up as a young man and remembering it, it makes you who are today in my opinion (Respectable Adult) what interests me most about your upbringing is you also have knowledge of H-A-M radio experience , Now I have a good idea of what would happen if the Mavic operator with the Remote controller was to fly near the Base station and if the Mavic was to fly into the Transmission signal of the H-A-M radio . Hearing your opinion of what would happen to the RC and Mavic AC from
a knowledgeable actual Operator just to confirm my thinking would be greatly appreciated ?
FlySafe-FlyFree

 

[WEOTN]

There's nothing wrong with what you were / did when you were growing up as a young man and remembering it, it makes you who are today in my opinion (Respectable Adult) what interests me most about your upbringing is you also have knowledge of H-A-M radio experience , Now I have a good idea of what would happen if the Mavic operator with the Remote controller was to fly near the Base station and if the Mavic was to fly into the Transmission signal of the H-A-M radio . Hearing your opinion of what would happen to the RC and Mavic AC from
a knowledgeable actual Operator just to confirm my thinking would be greatly appreciated ?
FlySafe-FlyFree

You have to keep in mind this is a theoretical analogy, each scenario can and will be different. 2.4GHz is the resonant frequency of water, and is used by microwave ovens for best heating. Our Mavic uses 2.4 GHz frequencies. 2.4GHz and up begins to act like light as it bounces off of things rather than moves through them like HF VHF and UHF, which can enter and heat the body. Water vapor can absorb/scatter our radio signals. So it isn't totally wrong to think of our radios like flashlights. Think of how someone with a flashlight walks around the corner of a house. The brilliance you had with direct view suddenly drops down to reflected 'scatter' off of trees bushes nearby, other buildings etc. Yes you can see it but, BUT, it is much weaker and from multiple "sources". By the same token, for the guy that went around the corner to see your light, it will be scattered off of reflecting surfaces and much weaker.

Radio receivers have to have some rejection circuitry to reject RF junk from other sources, and it takes physical space to filter out unwanted frequencies, which the Mavic doesn't have much of. I have not seen specs on the radio capabilities, but feel certain that filtering isn't as good as a walkie talkie. This means that strong signals off frequency will begin to drown out your RC's signal and "swamp" the receiver. Think of the flashlight you're holding, pointing at the trees hoping the guy that went around the corner can see your light compared to yard lights etc. It's a useful analogy if not accurate. Like listening to a soft voice in a crowded restaurant, it can be done but it isn't optimal. It takes some quality filtering.

Using digital spread spectrum, which I'm guessing 2.4GHz radio control uses so multiple signals can use the small spectrum allowed (the reason transmitter and receiver need to be paired, they handshake to each other to find each other in all the noise) there's going to be multiple signals in the range the radios are set to operate in. When the flashlight is in direct line of sight it is easy to see it, once it goes around the corner, what you see is multiple reflections, in radio that is called multipath, which while each is 'valid' they can arrive at different times and create node and antinode reception strength. Think of your FM car radio on a weak station. you roll to a stop and it drops out. Creep ahead a foot and it's back. That is the effect of multipath node and antinode, signal timing adding to each other or canceling each other. This makes it tough on the Mavic when it's not in Direct Line of Sight.

If your Mavic stops and hovers to regain the controller and happens to be in an antinode, it may give up and land or RTH depending on your settings and the whims of DJI programming. It might also hear 'noise' and guess at an input that wasn't given and do who knows what. So, I'll fly in Direct Line of Sight, or send it off with a pre-programmed Litchi Mission so it will fly the pattern as instructed whether it can communicate with the RC or not. Doing otherwise is a gamble which my $1000 isn't worth the payoff of pretty pictures.

I'm sure many can tear apart this analogy, but it is illustrative of the situations that can cause Mavics to do the crazy stuff that gets reported here. Again, this is an analogy to communicate some of what is going on in the RF spectrum that our senses cannot detect. I am not a physicist nor engineer so be kind. I'm just trying to help, not counter anyones choices.

 

[Karl2951]

All advice appreciated guys, i will try to make sure i wont go behind things just to be sure.

 

[SkunkWerx's]

You have to keep in mind this is a theoretical analogy, each scenario can and will be different. 2.4GHz is the resonant frequency of water, and is used by microwave ovens for best heating. Our Mavic uses 2.4 GHz frequencies. 2.4GHz and up begins to act like light as it bounces off of things rather than moves through them like HF VHF and UHF, which can enter and heat the body. Water vapor can absorb/scatter our radio signals. So it isn't totally wrong to think of our radios like flashlights. Think of how someone with a flashlight walks around the corner of a house. The brilliance you had with direct view suddenly drops down to reflected 'scatter' off of trees bushes nearby, other buildings etc. Yes you can see it but, BUT, it is much weaker and from multiple "sources". By the same token, for the guy that went around the corner to see your light, it will be scattered off of reflecting surfaces and much weaker.

Radio receivers have to have some rejection circuitry to reject RF junk from other sources, and it takes physical space to filter out unwanted frequencies, which the Mavic doesn't have much of. I have not seen specs on the radio capabilities, but feel certain that filtering isn't as good as a walkie talkie. This means that strong signals off frequency will begin to drown out your RC's signal and "swamp" the receiver. Think of the flashlight you're holding, pointing at the trees hoping the guy that went around the corner can see your light compared to yard lights etc. It's a useful analogy if not accurate. Like listening to a soft voice in a crowded restaurant, it can be done but it isn't optimal. It takes some quality filtering.

Using digital spread spectrum, which I'm guessing 2.4GHz radio control uses so multiple signals can use the small spectrum allowed (the reason transmitter and receiver need to be paired, they handshake to each other to find each other in all the noise) there's going to be multiple signals in the range the radios are set to operate in. When the flashlight is in direct line of sight it is easy to see it, once it goes around the corner, what you see is multiple reflections, in radio that is called multipath, which while each is 'valid' they can arrive at different times and create node and antinode reception strength. Think of your FM car radio on a weak station. you roll to a stop and it drops out. Creep ahead a foot and it's back. That is the effect of multipath node and antinode, signal timing adding to each other or canceling each other. This makes it tough on the Mavic when it's not in Direct Line of Sight.

If your Mavic stops and hovers to regain the controller and happens to be in an antinode, it may give up and land or RTH depending on your settings and the whims of DJI programming. It might also hear 'noise' and guess at an input that wasn't given and do who knows what. So, I'll fly in Direct Line of Sight, or send it off with a pre-programmed Litchi Mission so it will fly the pattern as instructed whether it can communicate with the RC or not. Doing otherwise is a gamble which my $1000 isn't worth the payoff of pretty pictures.

I'm sure many can tear apart this analogy, but it is illustrative of the situations that can cause Mavics to do the crazy stuff that gets reported here. Again, this is an analogy to communicate some of what is going on in the RF spectrum that our senses cannot detect. I am not a physicist nor engineer so be kind. I'm just trying to help, not counter anyones choices.

Your answer (Opinion) is appreciated there is no need to be a physicist or engineer with me I even seen that they can be proven wrong by someone with a HS diploma and experience of the issue at hand .
WEOTN, Thank you for your time and simplified answer