On another note, at work, funny thing... instead of the antenna, which looks very similar to the Arrow Antennas is not mounted on top of the tower, but inside, and sideways!?!
It points however, directly towards the terminal which the majority of the aircraft we talk to are at.
That is not a very good idea unless.......
Reasons to mount a ground plane antenna inside tower:
1) Doesn't know any better.
2) Lightning protection
3)Received signal is so strong that it doesn't matter.
4) Can't get anyone to climb to the top.
5) The only place left on a crowded tower.
If you look at the radiation pattern of a ground plane antenna, minimum signal strength occurs at 90 degrees from the horizontal, or directly above the antenna. So if your work GP is pointed horizontally at the signal source, it is receiving directly off the top at minimum signal strength. Not very effective. But if it's only used to send/receive across the field, it won't make much difference, the receiver(s) will still be saturated. Transmit SWR, however, will be high with all that tower metal near the radiator, making for inefficient power loss both TX and RX.
If you get a chance to ask someone in the know, I would be interested to hear their reason to mount it that way.