Originally Posted by msev
The guy with the low range uses a two battery setup, so there shouldn't be interferences through the wires, if its not connected to the motor..right.
It sounded alike, but he uses a UBEC, alas a DC/DC converter to power the HF module (at least that's how I understood), so either ripple and or harmonics caused by that (or other on board components) could have disasterous influence.
I would rip the vtx and camera out, provide a clean 3.3v source and do a ground test. Should give a clear answer. If this works, then add the UBEC and so on up until the source of the problem is found. If it does not work, replace the camear also to exclude that too and so on.