I'm a quadcopter FPV addict, and I'm building a new one.
As pointed out i will first explain some acronyms of the rc world
- PDB (Power distribution board)
- CCD (Type of camera sensor, cmos
ccd… not really relevant to the question) - BEC (A filtered voltage
regulator) - PDB (Power distribution board)
- VTX (The video transmitter)
Usually, the video transmitters receives power from regulated 12 V or directly battery voltage (usually 7 V to 24 V)
Most of them also have a 5 V output that is really useful to power the camera.
In this case I'm using one really similar to this one: 
As you can see it does not have 5 V output so I'm using a good CCD camera that needs 12 V that will be provided by a separate BEC on the PDB.
My question is, the VTX (The video transmitter) has two different grounds, i suppose one is the 7-24 V power ground, and the other is the ground of the 12 V camera power.
As the VTX does not provide power to the camera, does it really need to have the camera ground? The camera will have the ground from the 12 V BEC and the VTX has the ground from its VCC power.
I could test this when some final parts arrive but if it does not work i will need to resolder a lot of things and i would like to avoid that.
Also the 12 V BEC already has a lot of things on its small pads so i would like to avoid soldering another ground to it.
EDIT
My PDB is something like this:
My camera is already on the 5V BEC and the VTX on the VCC pad so its not filtered and that will induce noise in my VTX right?
Can i say that i can solve it by using the other 12V BEC to power the VTX
OR
Conecting the second VTX ground to the same 5V BEC the camera is grounded to?
Best Answer
FPV = First-person video? CCD = Charge Coupled Device. BEC = Battery Eliminator Controller? PDB = Power Distribution Block? VTX = Video Transmit? Not everyone knows what these acronyms stand for.
The top ground is probably "signal ground" for the video and audio, while the bottom ground is likely power ground. No datasheet was linked and googling "TS5840" finds only Chinese sellers.
Since a craft such as this contains several powerful electric motors, "power ground" is likely very noisy. Connecting all grounds together will probably work, but the result may be less appealing than expected. "Signal grounds" (if that's what it even is, cannot tell) are provided for a separate ground which carries less of this transient noise, which could affect signal quality.
If it were my aircraft, I'd wire signal ground right to the same ground the camera is using. Hopefully the camera is powered from something providing it's own ground, like a 5v regulator. Typically, low-ESR capacitance is provided on both the input and output of regulators, so I'd expect the ground there to be less noisy than say, connecting directly to the battery negative.
If you find the image quality to be lacking and suspect noise, try adding some capacitance across the +V and ground as close to the transmitter and camera as possible. A 10nF ceramic and 1uF tantalum cap (in parallel) on each should do a decent job of filtering power to them.