For fpv newcomers, getting good video transmission from craft to goggles is often a challenge. Understanding how the different parts work together is important for solving video issues, hence this post.
Video is a system, not one single component
If you want to have good video, you have to plan for the type of flying you want. There is no perfect video solution that fits all flying styles. I am going to focus mostly on long range, an application in which you fly far without obstructions.
For long range you want a good directional antenna and a decent receiver. I have tried a bunch, too many to name here. As of this post (December 2018) my choice for the goggles is the Eachine Pro58. The best budget antenna I know is the x-air, and if you really want to go far the x2-air is the best I’ve flown. Of course a good directional antenna won’t help if you don’t keep it pointed at your craft as best you can. I have seen many people fly with their antennas pointing to the ground. If you tend to do that, adjust your extension accordingly so that the antenna points towards where you expect your craft to be.
The omnidirectional antenna in your diversity receiver doesn’t matter as much for range, it’s only important when you’re flying behind yourself or to the sides. When you’re flying fast and close, you can’t always adjust your head quickly enough; an omnidirectional antenna has you covered in those situations. As soon as you gain some distance, your angle to the craft does not change that quickly. That’s when you want to make sure to track it with your directional. This takes a bit of practice, it involves gently sweeping your head side to side and up/down until you find the best position.
There are several good options for transmitters. I do not believe anyone should have to pay more than $25 for a 5.8 transmitter capable of ultimate range. I’ve flown 7 miles with a $9 AKK. This transmitter has fixed 600mw power and just the basic features (channel / band selection). If you need bells and whistles like smart audio and different power settings, you can go with other AKK models such as the x2 ultimate. If you want to support TBS, the Unify is an equally good alternative.
If you fly long range, you often want 600mw or (very rarely) more. It’s very important to make sure your transmitter does not overheat. When a VTX overheats, it tends to reduce the power which means you will lose video when far away. There are several ways to achieve this. The easiest is to ensure good airflow, which easy on a quad. On a wing you want to expose one side to the transmitter to an external surface with air flow. If that’s not possible you can dissipate heat with a good heatsink.
Lastly, the antenna and its placement is very important. For an omnidirectional antenna, you want to make sure the radiation pattern is optimally directed towards you as much as possible and free of obstructions. On a plane this is usually easy to accomplish. On a quad it can be hard; it’s easy to put the frame or battery in between you and the antenna when you’re flying in certain directions. The general solution to this problem is to make your antenna as tall and as separated from the airframe as you can. For the typical antennas we use, you want to make sure that they stand vertical when in normal flight position.
There are other subtleties to getting good video but this should be enough for most people to get decent range. Good luck and happy flying!