How can DJI uavs get solid telemetry and video signal nearly 2x distance ?

Discussion in 'General Discussion' started by CrashALot, Feb 26, 2019.

  1. CrashALot

    CrashALot Member

    Oct 17, 2018
    #1 CrashALot, Feb 26, 2019
    Last edited: Feb 26, 2019
    As you might have read reports or seen via utube vids, how can a DJI P4 for ex. fly and have good signals so much further than yuneec (any uav) - especially IF there is a FCC limit to the power (mw) in transmit power ? (like similar in all countries)

    Personally i am sure they use more powerful transmitters, even an extra 100mw would make a large diff and likely more amplification of received signals too.

    So if true, then why does yuneec use lesser power for transmitters on most/all uavs ?

    Anyone have a tech/viable explanation ??

    TIA !
  2. CrashALot

    CrashALot Member

    Oct 17, 2018
    #3 CrashALot, Feb 26, 2019
    Last edited: Feb 26, 2019
    Thx for reply,
    here is a bit more of the OcuSync protocol/system.

    go down a few replies and a guy explains to a degree how the system chooses modes.

    I suspect that it is a combination of more complex transmission signaling, both complex to transmit and receive and interpret, plus the payload protocol is likely more robust and redundant, but it could be parallel payload (data) redundancies that would allow for quick recovery of missed packets (bundles) of data, which would allow reliability at the extremes, the more complex transmission signal and mode hopping as well as channel hopping giving improved reliability too - the system simply being a more robust system especially in electrical noisy areas.

    unless invented by dji it would cost more to license the protocol and more complex chips too.

    i did calculate a dbi tx spec on a dji model and it was a higher power than is supposedly being used by yuneec for any uavs using st16, iirc about 100mw which is significant when you may have only 300mw being used - EU use less wattage than does USA.

    wifi (801.11) is so pervasive it is very cheap and even mimo (multiple in multiple out & spread spectrum tx/rx - normal wifi) used most by most wifi versions, a different 'audience/performance' is being attempted, and most wifi is close communication as well, so complex/expensive systems is not necessary.

    also signal strength limits of uavs vs wifi, you can buy 2000mw or higher normal wifi adapters for pc use.

    of course i do not have all my question answered and will keep looking, will post if i find real implementation details.

    i have read elsewhere that the 2.4ghz telemetry is a yuneec specific protocol but may still use a more simple transmission scheme as it barely seems to operate further than does the 5.8ghz and the slightly better performance may simple be due to 2 antennas and maybe nothing more.

    I do find it surprising that yuneec did create the 5.8ghz telemetry backup to the 2.4ghz since most of us lose 5.8ghz before 2.4, but is a nice feature which just might never be used or by very few - likely a very busy 2.4ghz band area (or obstructions) and clear channels can not be found !?

    also, since a ST16s is used for H520/TH+ is there a new effort to improve transmission quality ? As also likely a faster basic cpu might have been needed - but still just a 16 channel controller.

    ps: i did find that for the st16 on TH, there are either 6 or 8 unused channels, and AUX button is unused on the controller thus ...... !!

    thx again !

  3. HarveyH54

    HarveyH54 Active Member

    Here in Florida, it's flat land, and not a lot of physical obstructions, other than buildings and trees. If you are following the rules, and line of sight, the transmissions are reliable. Now, on my first Q500, and new to the big-boy quads, I of course, had to test the limits. My first aspiration, was to fly the half mile down to the lake, so I could see if it was busy down there, worth loading up driving down there, or walking my dog down. Obviously, didn't happen, couldn't see the q500, and the video dropped out, before getting even half way. Basically, tools are designed for specific use, but we can stretch the limit some, and usually hope to stretch the capabilities some. I sort of view DJI as bad-boy drones, which isn't in their best interest to market them as such, but I'm pretty sure they are proud of it.
  4. CrashALot

    CrashALot Member

    Oct 17, 2018
    we humans seem to always go to the extreme. ;)

    also assuming someone who has 2.5mi reliable uav control DOES NOT MEAN THEY WILL EVER OR ALWAYS USE THAT RANGE, does it ?

    No the point of having a 2.5mi capability is that it will likely offer a nice reliable thru trees or between/behind a building or such and give a good distance of control.

    if a uav gets out of view, and if video fpv is good then possibly can discover location visually and watch how to get back into uav visual range &/or around obstacles.

    meaning, a range just gives a more reliable product, more chances to stay in control !

    and if you use waypoints/CCC like i do, the uav can get out of sight NOT too far away (you set waypoint height to 10 meters), but if communications is feeble, which yuneec seems to have chosen a feeble video link at least if not limited telemetry, then you can have a costly TOO LOW TO SEE, where the heck is uav, loss of uav and $$$

    of course if signal is still avail, then you can hunt down uav and recover, see how it all works to give a MORE RELIABLE PRODUCT/EXPERIENCE !!

    and it appears the reason yuneec communications is much less than dji is that for their higher end uavs, they spent MORE $$ on their transmission system and protocols.

    and btw, dji did NOT invent the lightbridge, ocusync tech, it has been around a bit in the RC world, this being prior to 2017.

    ps: after 1/4mi i can barely see a uav or maybe even not at all in some light conditions, how about you ?

  5. HarveyH54

    HarveyH54 Active Member

    I'm good for about 500 feet, maybe a little more, depending on conditions. I have to know where to look for it, and have lost it a few times. Obviously 2.5 miles is overkill, regardless of the reliability excuse. I really prefer to keep an eye on my bird. Already destroyed one q500, don't wish to add to the junk pile, I learned. It's like buying a fast car, you aren't going to drive it fast, tickets are expensive, and you don't want to wreck it, but you are still are going to get on the gas peddle once in a while, just because you can. Think most people who get a new toy, will want to test the limits a little, you have to know what it can really do. The specs, and the marketing literature aren't usually very accurate, reality usually falls short, and you sort of need to know by how much. Batteries are really bad about it, and a few minutes can mean a whole lot.
    Codestar7 likes this.
  6. Sureshot

    Sureshot Member

    Feb 21, 2019
    Cleveland TN
    The amateur radio guys have a saying: "A dime of antenna equals a dollar of radio".
    In our case we would have some trade-offs.
    High gain directional antennas on the ST16 are a first step, but you will have to aim the TX to the plane.
    An efficient fixed position 5.8gHz video antenna on the Typhoon H will add range, but will limit camera pan.
  7. Mario Rodriguez

    Dec 24, 2016
    Miami, FL
    I can go about 2000 ft, but if I take my eyes off the bird and look down at the screen, bye bye birdie, almost impossible to see again. My first quad was a Q500 4K, still miss it, sold it as the range was just .... well ....lame and the camera was well, about the same. So I purchased a DJI Inspire 1 Pro now Raw for at this point almost 10 times the money, yes I've done a thing or two to it, unfortunately the Inspire unlike some of it's siblings does suffer from image transmission issues due to many vaccinations ( f/w updates) gone wrong which turned as I understand, a phenomenal bird into a lame one. However my most successful journey (limited by my stupidity as I forgot to replace the "test" battery for a 100% full) was a little over a mile over the waters of the Indian River/Biscayne Bay in Miami, FL but it was an anxious mile, full of warnings signal losses and almost soiling pants. So 6 of one ..........
  8. mk2112

    mk2112 New Member

    May 7, 2019
    Dji mavic and inspire have ocu-sync transmission which compresses the WiFi signal to a digital one, that is how they get the great distances.

    Sent from my SM-S337TL using mobile app
  9. Codestar7

    Codestar7 Active Member

    Nov 14, 2016

    Ditto all that.
  10. BigA

    BigA New Member

    Jan 14, 2019
    I can speak from experience here in the UK using the H520 with an E90 camera. The Control antena's are good for mile, and while the H520 is travelling away from you, the video also hangs in for about a mile.
    When you turn around to return at a mile away the fun starts, because the video antena is low down on the back of the camera and can't be seen by the S16 controller, when the camera is looking towards home. So you lose or only get intermitent video. What can you do?
    Fly back with the H520 still facing away from you untill about half way home. It works
    Bring the map up on screen, you still have control and using the gps, and compass which I find I am still receiving when working a mile away. While doing this ignore any flashes of intermitant video which will not be current and up to date.
    Finally give the machine a chance and raise the landing gear after any take off. With the gear down the antenas will not get a clear shot to the controller.

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