Covering LNB will reduce signals in rain.... I experienced it......Never cover the LNB in my opinion...... Line of sight should be clear and use good quality coaxial cable......
Warpage will cause signal mis-reflection and you won't be getting the best performance out of your system. So take care of your reflector and dish fittings,never mishandle it.
A low-noise block downconverter (or LNB) is the receiving device mounted on satellite dishes used for satellite TV reception, which collects the radio waves from the dish. Then change the higher frequency to lower range.
And all processes including amplification and down converting is at least attenuation/noise possible.