I used a Matrice 400 to act as an aerial relay to fly my Matrice 4T extremely low and far !! You won't believe what an aerial relay is capable of.

[cgmaxed]

Since we , in the USA, can't use those wireless 4G dongles DJI makes, I decided to try the aerial relay method. In my case, I used the M400 as the aerial relay drone, and the M4T as the main mission drone. The most impressive thing I want to tell you all is the M4T mission drone was able to fly to it's max battery limited distance (which i won't say on this forum, I'll let you all find it online). That's all good and dandy, everyone has done range tests, but they have to keep increasing their altitude the further away they get, unless they are on a 9th floor balcony. THE KICKER HERE? I was able to fly from street level, while the M4T mission drone flew at a constant altitude of 75 ft AGL and returned at the same altitude, from it's battery limited range.

Most range testers from street level hit 400 ft or higher to maintain a connetion, thus you can't collect detailed ground DATA because they are too far away (too high) from their areas of interest. With the Matrice 400 hovering above me at 250 ft, the signal was maintained with no signal loss during the entire 75 ft AGL flight. What's also good about being able to stay low, is that the M4T did not lose excess power due to high winds, which occur at higher altitudes. So i was able to save battery, increase distance and stay low to film more detail. Also staying low, lowers risk if hitting manned aircraft, except some heli pilots who fly lower than 75 ft. In addition, the M400 had the DJI ZENMUSE H30T camera on it w 400x zoom., which alowed me to visualize the M4T through its entire flight. The M400 acts like an observation tower as well as a relay station. NOTE: DURING THE M4Ts FLIGHT, THERE WAS NO LOSS OF IMAGE OR CONTROL TRANSMITTION BETWEEN THE M4T AND ITS REMOTE CONTROL UNIT.

IN CONCLUSION, the M4T got longer flight time, longer range, no signal loss, and collected highly detailed low altititude data, at any distance (battery limited) away from its take off point. Also, (better than no VLOS at all) the M400 was able to maintain DIGITAL VLOS using the DJI ZENMUSE H30T's AI assisted TRACKING of the M4T through its entire flight (visualized by 400x zoom). Yes, the M400 was able to track the M4Ts entire 75ft agl flight, assuring constant situational awareness, albeit through digitally tracked live video from the M400, zoomed in and locked onto the M4T through it's AI tracking function.

The future is in AERIAL DRONE RELAY SYSTEMS. No need for cellular dongles.

Digitally/ Electronic AssistedBVLOS supporter. Given AI assisted tracking and clear video of the BVLOS drone and it's surrounding environment. SAY YES, TO DIGITALLY ASSISTED SITUATIONAL AWARENESS.

 

[jaja6009]

Thank you for the feedback!

This could be a huge improvement for situational awareness for many industries. In Public Safety, the newest COAs that allow for BVLOS could definitely use this to their own advantage and enhance safety.

I am very unfamiliar with using this relay function though.

I know you can do it with the new DRTK 3, and now I know you can with the M400. Can you use a Matrice 4 series as the relay also?
I am very impressed with the H30T, we have the H20T and have been wanting to upgrade, so maybe we should make the leap.

It's pretty amazing that the H30T could track such a small aircraft from flying at 250 ft AGL, especially when looking down with ground clutter.

We do have a Matrice 4E and 4T, so if the relay function works with a Matrice 4 series drone we may test this out in the near future.
With our new BVLOS COA this could help out big time when flying BVLOS and the RPIC not being in an elevated position like on a roof.

On a side note, how was the M400? We have a 300. Anything else that the M400 can do that you tried out and want to share.

 

[GadgetGuy]

11 mile control range via relay! Love the relay concept and the creativity, but the M400 with that lens is a $15,000 "dongle," which is still limited to LOS, equivalent to flying from a 250 foot hilltop over lower ground. It still won't help maintain signal when flying behind any tall structures along the route, that may be necessary for nonlinear missions, which is the primary purpose of the 4G dongles in urban settings, rather than just longer LOS flights.

What's necessary to get a DJI dongle waiver in the U.S.?
LEO appears to have access to functional 4G dongles for their rooftop drones in a box for flying between and around intervening downtown skyscrapers.
Is Skydio the only company able to offer 4G dongle use in the U.S.?

 

[jaja6009]

11 mile control range via relay! Love the relay concept and the creativity, but the M400 with that lens is a $15,000 "dongle," which is still limited to LOS, equivalent to flying from a 250 foot hilltop over lower ground. It still won't help maintain signal when flying behind any tall structures along the route, that may be necessary for nonlinear missions, which is the primary purpose of the 4G dongles in urban settings, rather than just longer LOS flights.

What's necessary to get a DJI dongle waiver in the U.S.?
LEO appears to have access to functional 4G dongles for their rooftop drones in a box for flying between and around intervening downtown skyscrapers.
Is Skydio the only company able to offer 4G dongle use in the U.S.?

For a waiver, there is none. This would be an FCC issue, not FAA. The FCC did not explicitly ban the DJI 4G dongles, DJI just did not introduce them to the US, most likely due to the controversy that DJI has at this time. You used to be able to add the DJI Dongle to the controller for the M30 series and use it to access the internet. You could not fly using 4G, but at least you add instant internet for Flight Hub 2 for live streaming and uploading of video and images for distribution to required parties. This stopped working after a firmware update.

There are a number of 4G solutions available. The ones that I know of are Skydio, Parrot and various other companies that have proprietary 4G dongles for DJI aircraft, with Paladin being one I am very familiar with. Companies like Paladin have expensive annual contracts and the 4G dongles only work with their custom software, so if you don't pay the contract in a couple of years you lose your 4G ability. We were quoted ~$30K a year, but there was also maintenance, training and other perks added along with a dock version of the M30T and related M30T accessories.

You have great points on BVLOS and going behind buildings and on how 4G helps to mitigate this. We don't have a large sUAS budget and if a Matrice 4 series helps to get another Matrice 4 series further out, it could really help out in certain circumstances.

For us, we are going to move onto Skydio in the future, but I always will have a negative bias with them since I perceive them as being part of this whole DJI nightmare.

 

[GadgetGuy]

For a waiver, there is none. This would be an FCC issue, not FAA. The FCC did not explicitly ban the DJI 4G dongles, DJI just did not introduce them to the US, most likely due to the controversy that DJI has at this time. You used to be able to add the DJI Dongle to the controller for the M30 series and use it to access the internet. You could not fly using 4G, but at least you add instant internet for Flight Hub 2 for live streaming and uploading of video and images for distribution to required parties. This stopped working after a firmware update.

There are a number of 4G solutions available. The ones that I know of are Skydio, Parrot and various other companies that have proprietary 4G dongles for DJI aircraft, with Paladin being one I am very familiar with. Companies like Paladin have expensive annual contracts and the 4G dongles only work with their custom software, so if you don't pay the contract in a couple of years you lose your 4G ability. We were quoted ~$30K a year, but there was also maintenance, training and other perks added along with a dock version of the M30T and related M30T accessories.

You have great points on BVLOS and going behind buildings and on how 4G helps to mitigate this. We don't have a large sUAS budget and if a Matrice 4 series helps to get another Matrice 4 series further out, it could really help out in certain circumstances.

For us, we are going to move onto Skydio in the future, but I always will have a negative bias with them since I perceive them as being part of this whole DJI nightmare.

As I have understood the relay marketing videos for the Matrice 4, with multiple aircraft, one could effectively create a 4G dongle effect with proper positioning of the one or more relay aircraft in the air to support relaying signal behind or over intervening obstructions that would otherwise block LOS signal from controller of the primary drone. If you want to fly on the back side of a hill, you would merely need to position a relay drone above the hill to relay the signal from in front of the hill to behind the hill. If you already own the needed extra Matrice 4 unit(s), using them as relay units is a great way to leverage that investment in new unique ways.

 

[cgmaxed]

Thank you for the feedback!

This could be a huge improvement for situational awareness for many industries. In Public Safety, the newest COAs that allow for BVLOS could definitely use this to their own advantage and enhance safety.

I am very unfamiliar with using this relay function though.

I know you can do it with the new DRTK 3, and now I know you can with the M400. Can you use a Matrice 4 series as the relay also?
I am very impressed with the H30T, we have the H20T and have been wanting to upgrade, so maybe we should make the leap.

It's pretty amazing that the H30T could track such a small aircraft from flying at 250 ft AGL, especially when looking down with ground clutter.

We do have a Matrice 4E and 4T, so if the relay function works with a Matrice 4 series drone we may test this out in the near future.
With our new BVLOS COA this could help out big time when flying BVLOS and the RPIC not being in an elevated position like on a roof.

On a side note, how was the M400? We have a 300. Anything else that the M400 can do that you tried out and want to share.

Setting up the relay: Only the M400 showed the relay transmition function on it's screen when I turned both drones and RCs on. Setup was simple. You have to update the firmware of both drones and RC components. Then, you turn on both drones and RCs. On the openning page their is a choice to use the drones as the relay unit or the main mission unit that receives the relay signal. I noticed only the M400 had the option to act as the aerial relay drone (in my case using two different drones), The M4T didn't show the relay transmitter option in my situation, when used with the M400. It only had the option to receive the relay signal and act as the mission drone.

Once you press the option on each rc for one drone to act as the relay and the other as the receiving mission drone, you press "LINK" on both RCs. Threy link and you launch the relay drone 1st, then the receiving mission drone. Then, you place the relay drone in a spot where you know the two drones will have no buildings or objects between them. If you have to fly the mission drone behind something, you just move (using altitude and/or horizontal repositioning) the relay drone to another position so the 2 drones no longer have an obstacle between them.

I'm not sure but, I think the reason I was limited to only M400 as Relay and M4t as receiving drone because they are different model drones with different firmware. I've seen, in the new M4T firmware features, that they have been given the aerial relay functions, So, maybe if you had 2 M4Ts they could be used as both relay transmitter and receiver mission drones, as they are they same units.

SINCE YOU MAY HAVE MORE THAN JUST ONE M4 E and/or T, update both machine's firmware, then turn on both drones and RC units, If they have the aerial relay function, you will see "relay" and "mission" options on both Rcs as options when the APP opens, then you can chose which M4 you want to use as aerial relay and Mission Drone. Then press "LINK" on both RCs after you assigned each drones function. The firmware update I saw didn't indicate if the M4 series aerial relay function needs a D-RTK ground relay unit. So, the best thing to do is what I previously said, using two M4s to see if the options show up on screen without a D-RTK relay ground module.

REGARDING SITUATIONAL AWARENESS: The M400 with the M4T as the mission drone is great because of the M400 with the Zenmuse H30 Series Camera is a 32x optical with 400x digital zoom, can see the M4 most of the time and track it, but sometimes loses tracking, HOWEVER, on the M400s screen there is a Blue Box that Shows you where the Mission drone is at all times. So, if tracking is lost , you just zoom into the blue box. Also, regarding situational awareness, seeing the blue box on the the relay drone'S RC screen, lets you know where the mission drone is and visualize the entire area around it for miles. You will definitely see any aircraft approaching. This allows you to lower the Mission drone to 45 ft using the relay drone, thus keeping the mission drone out of the flight path of any oncoming or nearby manned aircraft.

You Last question: I haven't used the M300 or 350. Just the M400. Its's faster, 56MPH. Its battery really does last up to 53 minutes with just the Zenmuse H30 as its payload. It's propellar arms open and can be locked in less than a minute, same for folding them. I tend to leave the legs on and just put it in my trunk when going somewhere. The battery system is amazing. The battery has a handle, when grabbed and pulled up, it unlocks the battery from the drone and it slides up and out, then you slide it in the charger and close the handle to charge quickly.. The anti collision radar literally will not let you hit anything from power cables to twigs of the same radius. It's landind accuracy is about 1.5 inches from the takeoff point when using RTH to land. But I don't depend on it, I always land manually, after RTH gets me close enough to the the landing site.
OH, THE 04 OCCUSYNC SIGNAL: The M400 has the best signal of any DJI OR AUTEL drone I have ever used. It's better than M4T, Mavic 4 Pro, and all previous matrice or enterprise drones I've used, and better than Autel"s Alpha Drone (which I used) but am selling.

 

[jaja6009]

Great information!!

We have a dedicated drone training day coming up. We will test the relay function with a 4E and 4T.

 

[cgmaxed]

Great information!!

We have a dedicated drone training day coming up. We will test the relay function with a 4E and 4T.

Any news on the testing of 2 M4 models? Did they both show relay and mission options on both Remotes? Grok AI researched all available internet DATA FOR ME. Saying when 2 or more M4s are used together both Remotes will show a Choice for relay and a choice for mission drone.

HERE IS GROK AIs answer to my query WITH SURCES:

MY Inquiry : Do the DJI M4 DRONES have relay and mission drone choices when two M4S ARE USED TOGETHER?

GROK AI: YES ! , the DJI Matrice 4 Series (including models like Matrice 4T, 4E, and the dock-compatible Matrice 4D/4TD) supports a relay drone function when using two compatible drones together. One drone can act as a relay aircraft (hovering at altitude for line-of-sight) to extend the control and video transmission range of the other mission drone (the primary aircraft performing the task), particularly in obstructed, mountainous, or no-4G areas.


This feature is configured via the DJI Pilot 2 app on the remote controller (typically DJI RC Plus 2 Enterprise): link each drone to its own controller, then designate one as the Main/Mission Aircraft and the other as the Relay Aircraft. It enables extended operations beyond standard transmission limits.


The standard Matrice 4T/4E models support multi-drone operations (e.g., synchronized livestreams via DJI FlightHub 2), but the onboard airborne relay is prominently featured in the Matrice 4D Series (designed for DJI Dock 3 integration).

Key Sources​

• Advexure: Matrice 4D Series Guide — Describes one drone hovering as relay for another.
• Advexure: Product FAQ — Details setup in Pilot 2 app (Main vs. Relay).
• DSLRPros: Matrice 4TD — Notes one aircraft maintains communication while another executes the mission.

 

[cgmaxed]

Now that I know the M4 series drones ,when used together, can serve as both relay and mission drones, It's tempting to sell my M400. I'm not sure what I'll do. The M400 has or will have lots of future options. It's fast, and its flight time is amazing, great for an antenna. My M4T runs out of power about 10 minutes before the M400.

Here is how I perform my end of mission sequence. The M4Ts power runs out earlier than the M400. So, when the M4T reaches a need to RTH, I start the sequence beginning with the M4T. While the M400 is hovering high in the sky and near mission control, the M4T comes in and lands, usually within 1 inch of its take of point, night or day. I don't even wait for an RTK LOCK before takeoff. At night the landing accuracy is the same, I guess because my landing area is lit up in a 20 ft radius with daylight level illumination and it can use the optical assist method of landing accurately.

HERE IS WHAT I HAVE LEARNED SO FAR.

My M4 is an M4T. The thermal allows me to look back at the Matrice 400 in thermal mode when I get a warning that an Aircraft is near. Through the thermal lens of the M4T the M400 looks like a bright star. Any nearby manned aircraft are also visible within 2-3 miles of the M400 using the thermal on the M4T. I REALLY ONLY NEED TO CHECK THE M400 WHEN WARNED, BECAUSE IT IS FLYING AT 300 TO 350 FT. Putting it at higher risk of collision. My M4T is flying at 10 to 60 ft. I need not worry about aircraft collisions with it.

Also, using the M400 as an antenna that has to fly at a higher altitude, it's size and battery capacity keep it from losing power or moving around even in high winds. The M4T saves a lot of power, because I fly below the higher speed winds that you begin noticing aroung 60 ft and above. Si instead of being hit with a common headwind of 11mph, I can fly ow enough to reduce it to 5mph.

The thermal is a must on the M4. It can see heat signatures of aircraft to about 3 miles away, allowing you to respond to and danger quickly,

Another point. A BIG ONE! I DO NOT HAVE TO GO OUTSIDE. i CAN FLY THE MISSION AND RELAY DRONE FROM WITHIN ANY STRUCTURE OR CAR, WITHOUT ANY SIGNAL DISRUPTION. AS LONG AS I'M CLOSE ENOUGH TO THE M400, i CAN STAY INSIDE MY AIRCONDITIONED CAR, HOUSE, OR OFFICE.

RID****NO REMOTE CONTROL LOCATION DATA IS SENT TO RID. THE REMOTE CONTROLLERS CAN NOT RECEIVE GPS SIGNALS AND GET A LOCATION LOCK ON OPERATOR LOCATION, WHEN IN A CAR OR BUILDING. Thus, the remotes can not send RC Location Data to the relay and mission drones, keeping RID from transmitting the operators location.. Any Karen's wanting to know where the pilot is can't find the pilot, if you launch from a distance away from your operations center, or if you launch near your mobile vehicle, which is surrounded by metal, blocking satellite signals TO THE REMOTES' GPS RECEIVERS, AND THEN YOU MOVE YOUR VEHICLE SOMEWHERE ELSE, AND YOU CAN'T BE FOUND.

Hope you enjoyed and learned a few things from my experience.

Have a great day everyone, stay out of trouble.