Apologies if I'm wrong but nobody seems to have asked if there is a balun at the dipole feed point. If there is no balun the coax will be part of the antenna, which would explain lower frequency resonances.
There's also a question about height, at least for modelling. The antenna would have to be very, very tight or be supported along its length to remain 1m above ground. Is that the case or is it a V shape with higher ends?
73
Mike
