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Phantom 3 Wifi specs
13858 6 2015-6-19
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fredz
lvl.3
Flight distance : 6322290 ft
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Luxembourg
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I understand that the Phantom 3 uses wifi for Lightbridge live video. But what radio mode does it use for transmitting commands? Is this a mode that goes much further than wifi, so you can still fly if wifi stops working?
Actually the difference between "remote controller signal" and "hd video link signal" in the DJI App.
How does it work technically, would be great to have some good info!
2015-6-19
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aburkefl
First Officer
Flight distance : 78612 ft
United States
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I'm not an expert - if we're lucky, someone who knows more than I will come along.

The Phantom 3 is using Lightbirdge to provide the video feed back to you. It is NOT using WiFi. WiFi has a much, much more limited range and capability. According to comments from DJI employees, here's another major difference.

In most "add-on" FPV systems, the craft is controlled by freqs in the 2.4 GHz range (and is digital) and the video is in the 5.8 GHz range, but is analog. The signal controlling the craft is much less prone to interference.  With the Lightbridge system, DJI says this signal is digital and is much less susceptible to interference than the typical FPV analog system.

The RTH (Return to Home) function on your craft is initiated either by the user (i.e., pressing the button on the remote controller) OR in the event the controlling signal is lost - NOT the video signal!

If your Phantom is still in your line-of-sight and you lose the video signal, you should still be able to manually control and fly your craft back to your position. If the controlling signal (NOT the video) is lost between your controller and your craft, it will automatically initiate an RTH and attempt to return to what it thinks is the Home Point.

A DJI employee put it the other day - "...once you take off and are flying, if you lose the video signal, you can still fly." You're sort of "flying blind" but the controlling signal is still there, you still have control of your craft - you even have control of the video and still capability, you can change the elevation of the camera (the tilt of the gimbal) and shoot video and take pictures, etc. You just can't see what's happening until after you download the media from your SD card.

I tend to keep my Phantom very close. I think the greatest distance my Phantom has been from me (while in the air!) has been about 200 - 300 yards. At that distance, I'm already at the point where I can no longer identify the orientation of my Phantom. If I shield the glare from my mobile device and see the picture well enough, I can tell where my Phantom is pointing - that is more than enough for me to identify that I'm capturing what I want to capture with the camera.

otherwise, for the most point, when I glance down at my screen, I'm looking at the battery level (the battery in my Phantom) and making sure I'm not dangerously close to running out of power. When mine gets to 50% I really keep a close eye on it. Now that the "voice" has been brought back in the Pilot app, I'm sure eventually I'll hear the "....low battery...." warning. Having my Phantom only 200 - 300 yards away should give me plenty of time to head back before hearing the dreaded "...critical battery warning..." and having it start an RTH on its own.

I like having control and making sure it's doing what *I* want it to do.

I'll bet the following scenario has already happened a lot more than owners are willing to admit:

You've done everything on your checklist.
Motors are started and you lift off.
You fly around/over/under/by this huge tree/building/tower and - suddenly - you realize you can't actually see your Phantom. You think "...I'll be  able to see it again in  a few seconds..."

In just a few more seconds, the Phantom will recognize it has lost the controlling signal (the connection between the controller and the Phantom has been broken) and it will initiate the RTH ON ITS OWN! and then you start asking yourself "....oh s**t. Do I have the RTH failsafe height set high enough to clear that tree/building...?"

In a panic, maybe even before you actually see your beloved Phantom, you grab one of the sticks or push the RTH button, whatever - you have just now negated the RTH function - reversed it. The Phantom now thinks that YOU have regained control - at least it thinks there's a control link still there and you've taken it over.

How many situations like this result in another visit here and "....my Phantom just flew away...."
2015-6-19
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gregg1r
First Officer

United States
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The Phantom 3 uses the frequency range of 2.4-2.485Ghz. There are 11 channels available, however I don't know which ones are used by the Phantom.

The Phantom 3 Light Bridge does not use the 5.8Ghz frequency. The DJI Inspire 1 uses 2,4Ghz for controls and 5.8Ghz for video.

DJI was also encroaching on frequencies which they were not licensed to use and powering the transmitters beyond allowed by law without a license. That was the reason for the Inspire 1owners complaining about a reduction of video quality and control signal distance.

2015-6-19
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Jack57
lvl.4

Canada
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aburkefl@gmail. Posted at 2015-6-19 20:03
I'm not an expert - if we're lucky, someone who knows more than I will come along.

The Phantom 3 is ...

So let me get this straight, when the phantom loses signal/connection to the controller and you have no video on your device to see what's happening, the phantom initiates RTH on its own? Does it still fly up to its RTH height that you set? and by pressing any controls like the left or right control stick while it initiates  RTH on its own, will that stop the RTH? Thx
2015-6-19
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aburkefl
First Officer
Flight distance : 78612 ft
United States
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Jack57 Posted at 2015-6-19 21:47
So let me get this straight, when the phantom loses signal/connection to the controller and you ha ...

I think there's a common misconception here.

If you lose the video the Phantom does NOT start a return to home. The key factor in the Phantom doing this on its own is two-fold:
(1) the controlling signal (NOT the video signal) is lost - i.e., the Phantom is no longer receiving control information from your controller. Maybe the battery died, maybe you dropped it and broke it or a number of other possibilities - but now, it thinks it is flying along without anyone being in control Instead of just flying along until the battery dies, it tries to find its way back home.
(2) the battery reaches its pre-defined critical level. According to the user manual, at this point the Phantom has given up on you, the guy controlling the flight, and since you're in danger of running out of battery, it's going to try to land  - now!

The above #2 - is not my opinion, that's stated in the manual on page 14.

If you initiate RTH on your own - assuming there's enough battery power to get back to the Home Point, when your Phantom gets close, you can press the RTH button again, turning off that function, and land the Phantom safely, on your own.

If an RTH gets started and you don't see your Phantom - when the battery reaches that critical level it's going to try to land - no matter where it is!

Read carefully everything that's available on RTH and FailSafe - knowing what to do and what not to do could mean the difference in losing your Phantom or having it return safely.

Again - just because the video signal is lost does not mean that an RTH is going to start. Many users are reporting that their video feed gets interrupted - or has even gone blank. If the video stops, that doesn't mean your Phantom is going to stop. If your Phantom is 1/2 mile away and your video goes out - good luck. I've not let mine get that far out of sight, but, if I did and I lost the video feed, I'd press the RTH button and cross my fingers.
2015-6-19
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aburkefl
First Officer
Flight distance : 78612 ft
United States
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gregg1r Posted at 2015-6-19 21:00
The Phantom 3 uses the frequency range of 2.4-2.485Ghz. There are 11 channels available, however I d ...

The Phantom 3 Light Bridge does not use the 5.8Ghz frequency. The DJI Inspire 1 uses 2,4Ghz for controls and 5.8Ghz for video.

I was really ready to take you to task on this. Then I read it more carefully! I see now you're referring to the 5.8 GHz freqs for the Inspire. Many thanks for pointing that out.

For those who may be less familiar:

Lots of companies who provide FPV for quads, planes, etc., are utilizing 5.8 GHz to feed the video back to the ground. The signals they're putting on those frequencies are analog, not digital. Consequently, when there's a lot of FPV users (like at a "meet") someone has to monitor who's using what channels and keep the number of participants down to a manageable number.

At least one of the DJI employees generally present here pointed out one day that the signals being used with the P3 video are digital, not analog. That may well be why we get some good video (720P HD) to our devices. It also explains why (I think) DJI recommends not having a host of people all flying Phantoms in the same place at the same time. There's a lot going on within that range of frequencies.

By contrast - and kind of irrelevant here - the RC plane people who are using ONLY 2.4 GHz - utilizing a technique called spread spectrum - can have a ton of planes all up in the air at the same time without too much danger of interfering with each other.

Something in the way of a compromise will have to shake out. If we're going to have thousands of Phantoms up in the air and Amazon is going to deliver packages via quads (I'm not holding my breath!) somebody is going to have to figure out some new techniques or some new spectrum capabilities.
2015-6-19
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benkknight
lvl.1
United Kingdom
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aburkefl@gmail. Posted at 2015-6-19 20:03
I'm not an expert - if we're lucky, someone who knows more than I will come along.

The Phantom 3 is ...

can confirm that. i flew my phantom 3 not too long ago and the video transmission was becoming too weak for me to judge where it was (i made the mistake of not keeping line of site, yes that was stupid of me but it happened) and i managed to get it back by flicking the switch to IOC and holding the right stick down. it might also happen with RTH but i don't use it because i don't fully understand the whole hovering height thing in the advanced setting
2015-8-25
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