In this article I will share some tips on how to connect VTX, FPV camera and OSD that give me the good video quality, with minimum noise in the FPV feed.
|I compiled the specifications of all FPV cameras for mini quad in this spreadsheet.|
|I compiled the specifications of all 5.8GHz VTX for mini quad in this spreadsheet.|
How to Power VTX and Camera
The safest way to power your FPV camera is by your VTX, do this whenever you can.
A lot of VTX’s these days provide 5V outputs and most FPV cameras can take 5V as input. If you are already using a filtered power source for your VTX, the additional regulator on the VTX is extra filtering for your FPV camera.
If your can’t power the camera from VTX for some reason, the next best thing to do is use a filtered, regulated power source to power both the VTX and camera. It can either be a dedicated UBEC, flight controller, or PDB.
Power FPV system directly from LiPo?
The majority of FPV cameras and VTX’s these days can be powered directly by a 4S, even 6S battery. But the raw voltage tends to be noisy because of the ESC’s and motors it’s connected to. The noise can get passed through the PDB or flight controller to your VTX and FPV camera.
When powering your FPV system directly from LiPo, your video quality will largely depend on how noisy your motors and ESC’s are, and how well your camera and VTX can filter out noise.
Some high end VTX’s have beefy power filtering, but FPV cameras generally don’t. Perhaps you can get away by powering your VTX directly from LiPo, and power the camera from your VTX.
To minimize noise in your FPV video feed, you want to protect both of your camera and VTX from exposing to noise. It’s best to power them from a filtered and regulated power source.
Tips for Clean FPV Video
Every ground pin is different
Ideally, all ground pins are the same, but in reality that’s not necessarily true.
Ground pins are connected using a piece of wire, or a copper trace on a PCB. Any piece of wire or copper trace has resistance, capacitance and inductance.
Due to the resistance between two ground pins on a circuit board, there will be a voltage difference if there is a current flowing through them. Think of it as an extremely tiny resistor.
It might help by connecting the grounds of your VTX and FPV camera to the same pin.
That’s why on some FC’s there is an “AGND pad” which is a single ground pad for you to connect both your VTX and camera grounds to, such as the Betaflight F4.
Why connecting signal ground is important?
There is current going through the power and signal wires, and eventually it has to return to its source via the ground wires. That’s why it’s called a “circuit”.
When you have signal ground connected, the current doesn’t need to go back to its source through the power ground. Therefore the signal doesn’t get affected by noise in the power as much as without the signal ground. This way you can better “isolate” signal from the power.
This is especially important when you are powering your FPV gear directly from LiPo battery, and if signal ground is available on your VTX or camera.
It’s a common practice to solder additional low ESR capacitors to the power or ESC’s in our miniquads, it can considerably reduce noise in the power.
Further Reading: why and where to add low ESR capacitor in a mini quad?
When you are getting lines in your FPV video, try to fix your FPV setup’s power first by powering your FPV camera from your VTX. If that doesn’t work, then you can try adding a capacitor in your battery lead.
Another solution is to add an LC filter between the power and your FPV system, it can reduce the noise going into your VTX and camera.
Note that an LC filter serves a very specific purpose: it prevents the noise getting to your FPV system, but it doesn’t reduce the noise level in the power like a low ESR capacitor does.
Last Resort: Connect FPV Camera to VTX Directly
Don’t wire things you aren’t using, such as OSD or camera control. Unnecessary wiring might introduce noise to your video.
If you are not using OSD, simply wire your camera’s video output straight to your VTX and bypassing the video signal pads on the FC.
Getting “black” lines in the video?
“White lines” are usually noise related, while “black lines” are power related which might be caused by a power hungry VTX. Some VTX don’t do well with regulated voltage, and they can even struggle to deliver the desired output power.
You might find the issue to be worse at a higher output power such as 800mw than a lower power such as 25mw. If that’s indeed the case then it’s definitely related to insufficient VTX input power.
You can try powering your VTX directly off of the battery voltage without any BEC. If this does not remove the black lines, you might just have a defective VTX or camera.