First Person View
FPV (First Person View) is a very recent innovation in R/C model flying. A miniature video camera and video transmitter are installed on the aircraft, and you view the transmitted live video stream using either a set of video goggles or a monitor. You use this ‘cockpit eye-view’ to fly the aircraft, using your standard R/C gear.
Besides the fun to be had simply piloting a quadcopter using the FPV equipment also works perfectly for those wishing to use their quadcopter for aerial videography. Many quadcopter owners like to fit a GoPro or similar video camera to their machine, to capture aerial footage of their surroundings. A simple FPV rig allows the pilot to see this footage in real time, and so manoeuvre the quadcopter to get the perfect sequence.
The video goggles give you a totally immersive experience – it is like sitting right in front of a widescreen tv in a darkened room. For those with large budgets, HD options are now available – but just as with tv, the non HD equipment gives perfectly acceptable picture quality.
The key to getting started with FPV flying is to Keep It Simple (KIS) – you can add complexity later (if you want to) when you have got to grips with the basics. A simple set-up would be an fpv camera (or GoPro), a video transmitter (VTx) and a set of video goggles with integral video receiver (or a video screen with a built-in receiver). If you have 2.4 GHz R/C gear then to avoid interference with the video signal you will need to use a 5.8GHz video set-up. To power the camera and vtx you need a clean power supply. If the quad is not equipped with a dedicated feed, then the best solution is to use the balance lead from the main LiPo.
For the FPV gear, buy a ‘bundle’ from a reputable dealer and save yourself a lot of hassle. That way the channels will match, the power connectors will match, the antenna connectors will match, the antenna polarity will match, the voltages will match – basically all the traps for the novice will have been dealt with.
Look after your goggles! The most expensive part of an FPV set-up is the video goggles, especially if you go for a set with the VRx built in (which you should). The good news is you will never crash your video goggles. But you can easily spoil them: the video screens are viewed through magnifying lenses so that you get an enormous image. But if you leave your goggles on the ground or on a bench pointing at the sun on a sunny day – then those lenses will focus the sun’s rays on the video screens and burn out the pixels one by one…. The goggles are supplied with protective cases: use them!
Circular Polarised Antennas
Swapping the standard linear antennas on your video transmitter (VTx) and video receiver (VRx) for circular polarised (CP) alternatives is well worthwhile. Circularly polarised antennas reduce ‘multipathing’. This is the situation where the video signal is being received directly at the VRx, but also, other portions of the video signal are bouncing off objects and also being received at the VRx – but slightly delayed. This can create ‘ghosting’ of the image. The other advantage of circularly polarised antennas is that they reduce signal loss when the quadcopter is banked, as in a turn. Linearly polarised antennas work perfectly (and are in fact more efficient than CP antennas) when the transmitter antenna and the receiver antenna are both pointing the same way = usually straight up. But once you start banking your quadcopter, this perfect alignment is lost and the signal deteriorates rapidly. This does not happen with circularly polarised antennas.
On Screen Display (OSD)
The On Screen Display (OSD) is a device you install in the aircraft which then overlays information onto the video stream, effectively giving you a Head Up Display of the vital data. The OSD will normally have a GPS module and a current sensor, or will link in to the Quad’s sensors. So you will have live data on how high you are, how far from base, which direction to turn to get back to base, how much battery current you are using, how much you have used so far, etc.
Head trackers are great fun. A module is installed in (or attached to) your goggles, and then your camera is fitted on a pan and tilt gimbal mount in the aircraft. When activated, any movement of your head creates a similar movement of the camera, allowing you to have a look around at the scenery. Or if you are pylon racing you can monitor the pylon all the way around (they go out of sight at the critical moment if you use a fixed camera). It is best to ensure that some known part of the aircraft is in view when looking straight ahead, as head trackers can drift: you then just trigger the reset button when looking straight ahead and it refreshes this position as zero. Head Trackers invariably connect into the R/C transmitter buddy port and are activated with the spring loaded switch.
In order to maximise the range and quality of the video downlink, some pilots set up a ground station. This will generally include a diversity receiver – which is two receivers built into one box, and electronically rigged so that the receiver which is getting the better signal is the one fed to the display. As each receiver requires an antenna, this then gives the opportunity to use higher gain (effectively more sensitive) antennas. Higher gain antennas can be flat panel or Yagi style. But as the gain increases, so the radiation pattern becomes narrower – which essentially means a high gain antenna needs to be pointed at the part of the sky where the quadcopter is flying. So some FPV pilots will use two panel antennas, one pointing ahead and left, the other pointing ahead and right, thus covering the flying area to be used. Or one panel pointing upwind where the pilot wants to fly, with an omni antenna on the other receiver to cover circuit flying.
A tracking antenna does what it says. Using the GPS data fed down with the OSD information, the clever box of tricks knows exactly where the aircraft is. A high gain antenna is mounted on a pan and tilt mounting and the electronics drives the servos to ensure that the antenna is focussed on the quadcopter at all times.
If you are mounting a GoPro or similar on a stabilised gimbal, to get smooth video footage, then you will need a separate camera for the FPV stream. The FPV camera has to move with the quadcopter, so that you can see the aircraft’s attitude with reference to the horizon. Camera switchers (R/C controlled switches that allow you to select the video stream being transmitted) can be used if you also want to frame shots once in position. The early gimbals were servo operated – but they were never perfectly smooth due to the way servos operate in tiny steps. ‘Brushless gimbals’ use brushless motors and are very smooth in operation.
To get the best possible performance you need to make sure that your installation is done well; make sure that no metal objects (camera, speed controller, receiver, battery, etc) can block the signal in any orientation. Make sure that your receiver system is installed well, all antennas are on tightly and the receivers are being given the correct power. Make sure that nothing is blocking the Fresnel zone: you not only need a totally clear line of sight between the video transmitter and receiver, but you also need to imagine a cigar shape between the two antennas that must remain unobstructed for optimum results. Avoid flying near reflective surfaces such as water and buildings, to avoid multi-path interference (or use circular polarised antennas). Avoid flying near obvious sites of outside interference sources such as telecom antenna sites.
See the next section here: Drone Safety & Regulations