Unless, the Tropo systems the marines use are very different than the ones the army use, they do not point them straight up, it woul defeat the purpose. You have to angle bounce the signal off of the troposphere, and it a rather narrow angle, using hyperbolic antennas.
They may well be different, I don’t know whether they are or are not. As for “pointing the straight up” as you say, NVIS antennas are “near vertical” which means they are not pointed straight up. There is a shallow angle. NVIS antennas are also generally made with wire.