I just observed a phenom that I cannot explain, so I thought I’d ask here as my reading hasn’t come up with a clear answer.
I understand that for the coke-tennas and other cantennas of differing wavelengths that the can becomes ( emulates ) the ground plane in much the same way as the 4 radials of a spider antenna. I believe we are saying that it forms a surface that reflects RF signals, rather than an electrical ground, per se.
Once could have a flat plate, a car roof or whatever also serve as a ground plane. Where it gets fuzzy for me is the antennas that are wire or collinear, etc.- I have seen comments that they do not require a ground plane. I imagine that people mean that the real earth ground plane is employed. OK, so absent a local metal reflective surface, does the chassis ground and real earth become the ground plane ? And if you are on a laptop on battery ?
I don’t see how they would perform very well with a flat radiation pattern without a ground plane effect. In a sense, its always there.
I suppose my other questions are whether the size and direction of the ground plane affect RF, distance below antenna, whether the antenna models have a ground plane assumption ( eg perfect )