Amimon CONNEX UAV Monitoring Solutions

In many ways, the RC aircraft industry is responsible for pushing wireless video technology forward. Even before drones were really used for video recording, the first-person view (FPV) experience demanded a way to give pilots a view from the cockpit, so to speak, of their model aircraft. The staple for many years has been 5.8G transmitters (“video Txs”). 5.8G, of course, refers to the fact they operate in the 5.8 GHz range, which is preferred over 2.4G because 2.4G is what transmitters (that’s radio controllers) typically use. While the proximity of other 2.4G Wi-Fi controllers—say, at an air show—isn’t a problem, having two 2.4G devices or two 5.8G devices mounted right next to each other isn’t the best plan. Though it’s more directional than 2.4G, 5.8G can still blast a signal thousands of feet on certain systems, but you may need a HAM license if you do not want to fall afoul of the FCC.

These are analog systems in a digital world, which isn’t totally a bad thing. With analog there’s no “digital cliff”—the signal just steadily degrades as it weakens, as opposed to being all or nothing. Those old enough to know what “rabbit ears” are know what I’m talking about. Additionally, as the signal weakens, the effective bandwidth that the signal can carry gets reduced, which is part of the reason a bad Wi-Fi signal is so much slower. Since the source has to modulate the quality dynamically, which can’t happen instantly, dropouts are guaranteed as receiver and transmitter readjust. One might wonder, why both then, with digital at all? It’s because quality with analog is abysmal, even with a great signal. Hobby pilots using video just for FPV may be fine with this—they are used to relying on lots of other instrumentation to help them navigate, anyway. Where it’s not so great is in aerial imaging, rescue, or other applications that mandate the picture be as clear as possible. 

Indeed, digital HD solutions do exists, but they mostly use Wi-Fi or a something close to Wi-Fi as a method of signal transport. This means significant latency and frequent dropouts. When you download a Web page, a packet, if it was really needed, can just be re-sent. With video, a dropped packet is a dropout in the image. Error-correction filters can overcome loss to a point, but sustained signal loss means significant latency. And since a weak signal means reduced bandwidth, real-world performance may—judged in terms of resolution—come out worse than analog. This is where the CONNEX by Amimon steps in. A made-for-video solution, it aims to maintain a robust 1080p60 HD signal while supporting line-of-sight range of up to 3,300' (1000 m). And all with no measurable latency; that means latency of less than 1ms.

The CONNEX comprises two key components: the air unit and the ground unit. Calling the air unit the transmitter and the ground unit the receiver is conventional—following FPV tradition, but a bit misleading. As we’ll see, two-way communication is actually taking place, making both air and ground units two-way. The air unit provides a mini HDMI input for connection with the camera. The maximum supported resolution is 1080p60. Lower resolutions are supported, as well, including 720p and standard definition. Basically, whatever your camera needs to output, the CONNEX will have a setting that supports it. If you are operating in less than optimal conditions, you may want to consider setting the camera to output at a lower resolution to be on the safe side.

The ground unit reverses what the air unit does, featuring a standard HDMI port for your preferred monitoring device, be it field monitor, FPV goggles, even recorder for reference purposes. There’s a standard 1/4"-20 tripod mount on the bottom, making it convenient to place it on a stand or tripod, or support it with a small “table-top” tripod.

At 4.6 oz (130 g), not including mounting hardware, the CONNEX air unit is light enough even for many of today's compact multi-rotors. It accepts a wide 8 to 26V (3S to 6S) input power range, for easy powering directly from most flight batteries without the need for a battery elimination circuit (BEC). When used with the DJI Zenmuse Z15, installation is further simplified, thanks to the Z15 Kit. This kit allows you to mount the CONNEX on the rotating part of the Z15, keeping the gimbal free to rotate its full 360 degrees.

Since the CONNEX beams a data signal rather than an exclusively video signal, there is extra bandwidth for a telemetry and control to ride in parallel to the video portion. In particular, an interface supporting Futaba’s S.BUS protocol means the gimbal control signal can be piped from an S.BUS-enabled transmitter on the ground end back up to the gimbal. As of firmware version 2.0, you can also use a PPM (Pulse Position Modulation) code signal as a means of control. Using the same air-end module for both video and gimbal control has the added benefit of simplifying wiring, since both camera video output and gimbal control input connections terminate in the same spot.

Generally, you’ll need more than just a video image to stay on top of what’s going on. Telemetry is arbitrary flight data, such as battery voltage, airspeed, GPS coordinates, and altitude, that is supplied by the flight control system. One way to monitor telemetry is via a transmitter that has a telemetry receiver and status display on it. But for first-person view (FPV), one prefers to have the telemetry data superimposed over the video feed. This is known as OSD, for “on-screen display.” CONNEX supports one of the most popular telemetry protocols: MAVLink data. Also known as Micro Air Vehicle Communication Protocol, MAVLink bundles data into a C value type known as a struct, for easy, lightweight transport over the air. With the appropriate flight controller or MAVLink-enabled encoder, you can embed telemetry in the video downlink and view it as OSD. Compatible flight controllers include Pixhawk, APM, and ArduPilot on 3DR aircraft and, with firmware 2.0 or later installed, with the A2 and Naza flight controllers from DJI.

The CONNEX offers one feature analog systems fundamentally can’t—security. The CONNEX’s signal is encrypted with AES-128 (using RSA 1024 for key exchange). Much like secure Wi-Fi, this means the signal will be basically indistinguishable from noise if intercepted. For many users, encryption may seem unimportant. But for government and military application is often a sine qua non. As well, commercial productions don’t want passersby stealing footage, even if the footage happens to be some unauthorized behind-the-scenes. CONNEX is currently one of the few systems—including digital systems—that is secure.

The basic CONNEX starter package features an air unit/ground unit set, which come pre-bound together. However, additional ground units are available separately. In “Multicast” mode, you can bind up to four ground units to one air unit. This is means a dedicated display not only for the pilot and camera operator, but two more screens for other members of the crew, such as the director, as well. Like the air unit, the ground unit isn’t picky about its power source. 7 to 19V will do. More than likely this means power-tapping from a professional video camera battery—like a V-Mount or Anton Bauer. Alternatively, CONNEX offers an accessory battery plate for Sony L-Series style batteries. L-Series batteries are, perhaps, the most popular batteries known to man.

The UAV vertical has had access to wireless technology a lot longer than most video markets. But the technology was more a way to add an immersive element to flights than an essential tool, now that aerial imaging has, so to speak, taken off. Demand for high-quality solutions that aren’t simply repurposed consumer technologies, like Wi-Fi, is starting to spurn innovation toward high-quality, dedicated transmission. In this domain, Amimon with CONNEX is a true pioneer.