If you are relying on an FPV mode of flying then you need to get used to the signs of poor reception and predict what they mean and what kind of action to take. They are a warning of potential issues such as starting to get out of line of sight, of noise in the atmosphere interfering and when you see the signals you can start to get back into a place in the air where the signal is strong again.
If you have a video signal that is being transmitted on 5.8GHz – much of the DJI Phantom kit uses this:
- The signal has a tendency to drop out quickly with limited warning if you accidentally go out of line of site
- This signal also has low penetration capabilities so flying behind most things will cut the signal off quite quickly
- Be very careful therefore to avoid getting any obstructions in between you and your machine. This includes trees
If you have a signal that is transmitting on 2.4Ghz or lower frequencies
- The lower frequencies can be less prone to dropping out very suddenly.
- You should still be very careful to avoid getting any obstructions in between you and your machine.
- You can get a little more warning that the signal is degrading. This includes you losing colour in your image or interference starting to come in.
- If you are using antenna that are linear polarized (e.g. a Yagi antenna – not normally found with DJI Phantom kit as at 6th Dec/2014), then this can lose image if the aerial is tilted at a different angle from the quad. Sometimes when the quad is turning in the sky the two aerials angles are not aligned and you may see slight signal loss. Typically this will correct itself when you stop turning and the quad straightens up. Be aware of those signs and learn to distinguish them from more serious signal loss
Whatever your video transmission frequency practice doing the following to help you recognise signal loss starting so you can be better prepared to return to safety
- Find out what it looks like if you do start to get an obstructed signal. Essentially you want to start to make an obstruction with the video signal in a safe environment so that you can recognise how the image changes as it starts to happen. With those signals recognised then you are better equipped to notice them when you are on your flying missions and can take safe appropriate action. You can do this outdoors by giving your quad to your spotter for them to hold with it turned on to transmit the video signal – remove propellors for safety so there is zero chance of it accidentally being turned on and hurting them. You then walk off, say into some woods, behind some bushes etc. with your video equipment and look at what happens to the signal as it degrades as the obstructions appear in between you.
- At home, after removing the props for safety, turn your drone on so it is transmitting its video signal (making sure the video transmitter antenna is firmly plugged in otherwise it may burn out your transmitter). Look at your video signal so you can see what a strong signal looks like. Then you can move your quad around a corner or some more substantial obstruction so you can see the impact of this on your image and how the impact increases as you obstruct it further. Remember the signs for when you are flying.
- To simulate flying out of the range of your transmission, look at what happens to your video signal if you take your video receiver antenna off your goggles or ground station – this massively reduces their range. You can start with your drone close to your goggles or screen and move it away to see how the signal changes. Make sure that you only remove the video receiver antenna, NOT the video transmitter antenna (the one on your quad) as that may damage the transmitter. Through this you will get more information as to what the degrading video signal images represent
Remember you should not be flying so that there is a break in your line of sight between you/your spotter and your quad. The above exercises are to let you recognise the issues on the video image. Your other source is of course your spotter that should be giving you plenty of warning if it looks like you are flying out of line of sight.