Phantom 3 Lightbridge Frequencies

[BrandAL]

I copied the config file to my IOS device from itunes,. But when I go to ADD file it doesnt see the file, I enabled the hidden files so what I did was dragged the file into the files in itunes in the pilot app files, its there but I cant see it.. If I want to remove it can you tell me how to do this if I want to go back to the stock app .. Like I said its there and the MOD is working but for some reason the file is still hidden in itunes.. How would you remove the file so I can go back to the app with NO mod? Thanks for your help if u can.,

Itunes by default doesn't show hidden files. If you want to show the hidden files in the DJI GO app, then I suggest you download IExplorer for Mac (is not free !!). However is worth it because it will allow you to extract almost anything from your iPhone.

Don't quote me on this. But as far as going back to the original .DJI.Configs file, I guess you need to delete the app from your phone and re-install it. I have not yet test this. But when I switch between my iPhone (32 channels mod) and my iPad (Default) I go back to the default 8 channels.

P.s. I tried many ways to copy the original .DJI.configs file as a back up, but is nearly impossible. I suspect it's because the file is specially protected (-rw-rw-rw) and cannot be moved somewhere else.

 

[Chris Beukes]

Recently, I have taken a little time to profile the RF systems for the Phantom 3 "Lightbridge" system.

I have unlocked the application installed on my mobile device to be able to select all 32 Channels that Lightbridge offers. It should be noted that the channels outside the 2.4 Ghz unlicensed ISM band have been locked out by the more recent versions of the application to prevent illegal operation outside the ISM spectrum. Using a Rhode & Schwarz DDF007 receiver I was able to get a pretty good idea of how the system functions within the RF spectrum.

The Phantom 3 Advanced and Professional seem to be using two separate RF link systems. One system for control of the aircraft which operates in the 2.4 Ghz ISM band (exclusively) for control uplink, using spread spectrum and another system that can operate anywhere from 2.28-2.6 Ghz which is a GFSK (Gaussian frequency-shift keying) digital video signal for downlink of the video image. Both uplink and downlink systems appear to be using MIMO (multi-in-multi-out) diversity antenna systems with an RF output power collectively at ~750 mw for each system.

Below is a list of frequencies the GFSK video downlink system uses corresponding the the DJI "Channel" number. These are 10 Mhz wide channels with the center frequency being listed and 5 Mhz being occupied on either side of center.

CH 1: 2.285 Ghz
CH 2: 2.295 Ghz
CH 3: 2.305 Ghz
CH 4: 2.315 Ghz
CH 5: 2.325 Ghz
CH 6: 2.335 Ghz
CH 7: 2.345 Ghz
CH 8: 2.355 Ghz
CH 9: 2.365 Ghz
CH 10: 2.375 Ghz
CH 11: 2.385 Ghz
CH 12: 2.390 Ghz
CH 13: 2.405 Ghz
CH 14: 2.415 Ghz
CH 15: 2.425 Ghz
CH 16: 2.435 Ghz
CH 17: 2.445 Ghz
CH 18: 2.455 Ghz
CH 19: 2.465 Ghz
CH 20: 2.475 Ghz
CH 21: 2.485 Ghz
CH 22: 2.495 Ghz
CH 23: 2.505 Ghz
CH 24: 2.515 Ghz
CH 25: 2.525 Ghz
CH 26: 2.535 Ghz
CH 27: 2.545 Ghz
CH 28: 2.505 Ghz
CH 29: 2.565 Ghz
CH 30: 2.575 Ghz
CH 31: 2.585 Ghz
CH 32: 2.595 Ghz

As you can see, many of these channels are clearly outside the 2.4 Ghz ISM band, which is why they are locked out of the application. I have attached some photos of the spectrum analysis of these systems.

Image 23 Depicts the video downlink signal (10 Mhz wide peak)within the 2.4 Ghz ISM band with the controller FHSS signal peaks on either side.

Image 09 Depicts the controller operating within the 2.4 ISM band on the left (spread spectrum) and the video downlink frequency (1o Mhz wide) operating above the 2.4 ISM band in one of the "upper channels" on the Lightbridge system.

Image 16 Depicts the video signal operating just outside the 2.4 Ghz ISM spectrum with the controller occupying peaks spread across the 2.4 ISM band.

Image 22 Depicts the controller signal hopping across the 2.4 Ghz ISM band with the video downlink channel not shown.

Image 23 Depicts the video downlink operating inside with 2.4 Ghz ISM band along with the controller's frequency hopping activities.

Hi I have a very straight forward question. Will my Phantom 3 Adv hook up to the Eachine EV VR Googles, I believe running at 5.8ghz? Many thanks in advance.

regards
Chris

 

[Darmie]

Hi I have a very straight forward question. Will my Phantom 3 Adv hook up to the Eachine EV VR Googles, I believe running at 5.8ghz? Many thanks in advance.

regards
Chris

No Chris sorry. Now, if those goggles have HDMI in, then you can purchase a module and install on your radio that gives you HDMI out along with the standard USB going to your tablet or phone. If goggles does not have HDMI in, but has Video in then you can purchase an HDMI converter to RCA video and use that. Keep in mind although the video will look nice, it won't be HD quality.

 

[Vertigo]

Hi I have a very straight forward question. Will my Phantom 3 Adv hook up to the Eachine EV VR Googles, I believe running at 5.8ghz? Many thanks in advance.

No. Completely different technology. Different band. Different protocol. Different everything.

 

[GodFear17]

Great information! Now, amy word best ch to use for best range considering stock cut antenna length?

The lower the channel the better it'll carry. 2.2ghz in theory has better ranging that 2.6ghz.


Sent from my iPhone using PhantomPilots

 

[Vertigo]

The lower the channel the better it'll carry. 2.2ghz in theory has better ranging that 2.6ghz.

Better range in theory, but worse penetration (and bandwidth). Besides, much more important is what exact frequency the antenna's are tuned for (never found this info for the P3) and obviously, the chatter on the band. Closer to 2.6 is likely dead silent as its not even legal, where as 2.4-2.5 is crowded by things like wifi.

 

[GodFear17]

Better range in theory, but worse penetration (and bandwidth). Besides, much more important is what exact frequency the antenna's are tuned for (never found this info for the P3) and obviously, the chatter on the band. Closer to 2.6 is likely dead silent as its not even legal, where as 2.4-2.5 is crowded by things like wifi.

Range and penetration are better the lower the frequency. (where microwave frequency are concerned) This is why 2.4ghz penetrates better and has better range that 5.8ghz fpv video. 5.8ghz bounces off just about everything, whereas 2.4ghz will have better penetration compared to 5.8.

Antennas we use are hardly ever "tuned" to one specific frequency i.e. exactly "2.475 Ghz", besides the extreme precision that would take to make, it's not really wanted, as systems we use normally use a pretty wide band of frequency and the lightbridge system uses frequency jumping. So you'd want an antenna that is in band and it'll do just fine.

However, using a DBS linear antenna, you can actually test this and I have. CH 1: 2.285 Ghz will get you better range, in my testing I've found ch1-ch6 best for long range runs (2+ miles) in the city the "chatter" aka noise floor will be higher in the 2.4 range. When I fly in the city, I almost never lose video signal but will always lose control signal first, because the channel hack doesn't change the middle band the control signal uses(2.4ghz range). Channel hack only changes the video signal. (to my understanding) really really really wish this could be changed!

Now really to get away from the 2.4 (chatter) and get a clean noise floor, you really don't have to get to far way. 100-200 feet from a neighborhood will normally get you a clean noise floor. Just open up your channels in app, and drive around, parks are not always the best to fly at because many of them today have wifi access. But not all..

But test it yourself, 2.2ghz ch1-5 will get you the best video range. no doubt about it. 2.6 is normally very quiet, but so is 2.2 just about the same. If you get out of city wifi noise, chan 1 is always going to net you the best video range. When we talk about range, bandwidth is not the issue. Penetration isn't really either because when you fly 2+ miles even air moisture becomes a factor. Really, 2.4ghz is a great frequency, but no where near what 900mhz can do or 1.2-1.3ghz.

I use the TBS crossfire on my custom birds and at 915mhz it can easily get out 50-60 miles. Yes, miles! 90-100km! With it, my only limiting factor is battery. lol