And remember -- the roof of this building is 110m, so a horizontal antenna is high enough to have pretty good low angle radiation! See
Large buildings are not towers or poles. Buildings have a significant amount of large conductive metallic things and noise generating junk inside.
A simple vertical antenna has elevation pattern mostly determined by ground several wavelengths from the antenna.
A simple horizontal antenna generally has elevation pattern mostly determined by ground immediately below the antenna up to a few wavelengths out.
If the building has wiring and large connected metallic things under the horizontal antenna, it will act like a reflector. If the antenna is somewhat low to the roof (less than 1/4 wave or more above the roof), the elevation pattern won't be much different than a low dipole over flat earth. Most of the radiation will be beamed straight up.
A vertical also will have a null below the antenna, nulling building coupling for RF. A horizontal has maximum possible signal into and out of the building. Even with a 400 ft high building, a horizontal antenna a fraction of wave over the roof can be very disappointing.
73 Tom
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