I’m glad that you have found it funny…
I will reform the question:
When we make a downtilt to a directional antenna, we are actually decreasing the field strength of it’s main lobe.
How many dBs we need to decrease that field to achieve the minimum down-tilt?
for example, we want to scale an antenna down-tilt from 1 to 15. 1 is the minimum degree. How many dBs we need to decrease the field strength to scale it as one degree?