Yes, for a single antenna, vertical orientation is best.Would this orientation of mounting the receiver antenna work best? Pointing up vertically? It’s a monopole.
Hard to tell from the picture, you may have cut off your active element. If you have, it’s an easy repair, just remove the outer part of the lead. I remove a bit more than I need, when I have removed all of the frayed wires, I will trim the active element to the exact length.
The active element. It is the exposed wire at the end. This what you care about, it should be fairly straight. It needs to be a specific length and away from anything metal, carbon fiber or electronic (ESC & battery). Those items will block the signal. If you have a 90 degree bend in the middle of the active element you will cut your range. The black part (in this picture), you don't care about, can be any length, tie it in a knot, hide it in carbon fiber. It's just the antenna lead.
If you fray the shielding (the lead) you will allow unwanted rf signal in, which will kill your range. The antenna must be repaired or replaced. To repair, just cut off the frayed coax and solder the remaining coax back onto the Rx board.
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