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Which side of this dipole is ground?
(programming.dev)
My guess
The left sort of looks like the outside of the cable so I think that's ground.
Let me rephrase (your answer may be the same). I know with some antennas there is a "ground plane" type of element that should be on the bottom. For a vertical dipole is this not the case?
You do seem to be right. It should not matter in theory, but it may be better for the one connected to the center (right on this image) to be up.
Source: https://www.rtl-sdr.com/using-our-new-dipole-antenna-kit/
Weird that they don't elaborate. I flipped it last night and it seemed marginally better this way, so maybe there is some truth to it. Take this with a truck load of salt as it wasn't any sort of controlled experiment at all.
It has a choke on it, it's a little blurry but you can see it. Should it be moved closer? I saw a comment on rtl-sdr's blog suggesting it.