In our collective building lot we have an underground parking, in which a company recently changed a functional garage door system, since then the reception is a lot worse than before. (Like it doesn't open even when you stand 5 meters away from the antenna.)
The entrance to the parking is like a rectangular tunnel. The antenna inside the parking, is a single wire antenna, is 5 meters away from the garage door, 5 centimeters away from the tunnel wall and 50 centimeters from the ceiling, and pointing alongside the road, towards the metallic garage door.
I tried to remember my physics lessons, about electromagnetic waves in rectangular guides, and it seems to me that the antenna should be pointing up.
Can someone explain to me the rationale of making the antenna pointing the way it points?
 adding information : the frequency used is 868.3 Mhz. (Before it was 29.960 Mhz). I measured the emitted power of my remote 50cm away using some USRP with a +3DB log periodic antenna, and it reads a power level of about -70dB (No idea, if that's enough, but my car key on 433.92Mhz in the same setup reads at about -68dB, and works really good)
 I know in open air that single wire antenna emits best when pointed upwards, but here I'm wondering whether the fact of being in an underground (probably armed concrete), would explain the alongside the road orientation, (that why I was evoking 'rectangular wave guides')