This is a great question. There is generally a null point which extends from the top of the antenna such that if you were to point the tip of the antenna at some distant receiver, the signal would be greatly attenuated. It’s not eliminated completely for the same reason if someone is yelling but not facing you; signals can bounce or bleed around and still be intelligible.

When I think about antennas, I like to imagine a donut: 🍩, the antenna extends through the center and the actual donut is the radiation pattern. This is good for mental modeling, but in application there are more things which influence radiation patterns. It’s still a good start.

When an antenna is placed on its side, the closer it is to the ground, the more of its energy is directed into the ground (or it may reflect back and nullify signal coming from the antenna), but for handheld radios (which are most likely VHF or UHF), having sufficient line of sight is what’s needed to have the system work properly, and where one needs to occasionally go through walls or other simple obstructions, a little more power can be helpful.

When skiing as you mentioned, have you been having any difficulty communicating with others in your current setup?