The reason for all the questions is that building an antenna is an exercise in optimization. We need to know what we’re optimizing for or we don’t know what tradeoffs to make. For example, if you want to use an antenna to work DX from many directions, you might want to work towards a reasonably omni-directional pattern which the major lobe centered at a relatively low angle. If your goal is to participate in regional nets you may want to emphasize NVIS if the coverage is appropriate.

The questions concern more than just the antenna, but also propagation. If you launch a signal what will it take to get it where you want?

The most frequent cause of antenna failure is not technical, it’s not knowing what you want the antenna to do when you put it up. Many hams buy a dipole or a vertical or some other antenna just to ‘get on the air’. That’s fine in and of itself if that’s all you want and if you don’t care who you talk to. However, if you have a reason like attempting a DXCC or some other award, or contesting, or something else, you need to know what it is or you’re likely to put up an inappropriate antenna.

No antenna does everything, but some antennas are more general purpose than others. When you know what you want to do with it, you’ll know what antenna to put up.