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I found an old 2015 article about FPV wiring, and it had some informative diagrams. The article can be found here: https://www.truerc.ca/technology/fpv-wiring-tech
I pasted the essence from the article for easy reference. All of my wiring is similar to #4, and there is no noise, even with no LC filter but with caps on the batt and esc leads.
The worst situation being long and small wires from batt. to ESC and connecting the camera’s grd. near the ESC, as seen in img.#1.
Img. #1 “Bad video wiring”
A good wiring is shown in img.#2. As depicted, voltage ripples (noise) grow as you get away from the power source (batt.).
Img. #2 “Good video wiring”
Now, if we add the Vtx same thing apply. If we connect the Vtx’s ground at the camera, we will have the ripple from the cam on the Vtx ground line. Although, the ripple from the cam is very small to non-existent, it is good wiring practice to wire the Vtx at the source like in img. #4.
Img. #3 “Bad Vtx wiring”
Img.#4 “Good Vtx wiring”