Mesh In The Sky – Part (Mavic) 2

A few months ago, I used a low-end GPS-guided camera quadcopter to see how a micro-mesh node (the GL.iNet USB150) would work at altitude. This time, I experimented with a higher-end model, the DJI Mavic 2 Zoom.

After the field test we did in July 2020, a Ubiquiti NanoStation was temporarily mounted near the point we had tested on WJ0X’s end, and I permanently mounted my Rocket M2 over my garage door. Our two nodes could occasionally contact one another, especially at night, but any kind of inclement weather or daylight hours seemed to cause connectivity issues. Recently, I noticed the link had remained down for an extended period of time. This experiment started off with me trying to fly a similar payload to my last effort, with the intent to bridge our two networks temporarily with a small airborne mesh node to restore connectivity, if only briefly.

The DJI Mavic 2 contains a dizzying array of optical and infrared anti-collision sensors, so strapping things directly to the bottom of the vehicle will trip it up a bit. There are 3rd party accessories that allow for mounting things on the top or sides of the airframe in such a way to avoid blocking any of the sensors there, but I opted to just dangle the payload below the quadcopter with a length of fishing line. To attach it to the vehicle, I used a velcro cable-organizing strap I had laying around, positioned around the body in such a way as to not obstruct any of the sensors on the bottom. If you look closely to the right, you can see the thin, clear 4lb test fishing line coming off of it. This was tied to the center of the strap under the quadcopter.

The first payload was an old Goal Zero Switch 8 USB battery pack, with the same GL.iNet USB150 node plugged into it. I built a stabilizing harness out of zip ties, so that I could attach it to fishing line.

Craning the Mavic 2’s on-board camera downward, I confirmed that I was hovering between my QTH and Jay’s, and that I had a clearing beneath the vehicle so that if it had to land, or if the payload came loose, it would be both easily recoverable and not cause any damage to property. I was around 150 feet off the ground so that I could clear the rooftops of other buildings with line-of-sight between the payload and my Rocket M2 at home.

This is about the time I found out that Jay’s node had been taken offline until it can be permanently mounted on the roof. I guess I should have chatted with him on the morning net before trying this HIHI. I confirmed that the USB150 works just fine more than 1500 feet (450+ meters or almost 1/3 of a mile) away from my Ubiquiti Rocket M2 as long as there aren’t any obstructions. I hovered in this location for about 5 minutes before bringing it back home.

Last time, I said I’d think about flying with the GL.iNet AR150-EXT, a slightly more powerful travel-router, with an external SMA antenna connector, and a better antenna. The quadcopter I used last time would not have been able to hoist the payload easily, but the Mavic 2 seems to be able to lift half a kilogram worth of payload without any problems at all. With Jay’s node still offline, I am not expecting to make contact with another node. As was mentioned in my last “Mesh In The Sky” post, the nearest active nodes are 8 or 9 miles away, the kinds of distances you’d likely need directional antennae for. But I tried anyway. The AR150 and omni-directional antenna were attached to the battery pack so that when it’s lifted, the antenna points straight down.

You can see the approximate distance I put between the vehicle and the payload here. These are still connected to one another with fishing line, which is not easily visible.

I hoisted the payload up to an altitude just below 400 feet, which is the legal limit for most recreational unmanned flights of this nature. Again, I positioned the payload and vehicle somewhere a bit out of the way for the hovering maneuver so that potential damage to life and property is reduced.

While the payload dangled 400 feet in the air, I checked connectivity to the node above, this time with the USB150 plugged into my laptop. The AR150 remained connected to both of my AREDN mesh nodes at home but after hovering for about 8 minutes, never did pick up any of my distant mesh friends.

We continue to make headway, slowly, here in the Kansas City area, with frequent Zoom meetings to coordinate the setup of new nodes and discuss the results of site-surveys. Hopefully by next spring we’ll have some better mesh coverage through a few local hospitals and emergency operations centers.