depending on time of day,the satellite is in different positions as it rotates in orbit with the earth.
i have the antenna on the cab visor of my semi truck,certain times of day(usually very early am and very early pm) i get intermittent reception depending on the direction of travel,this is because the cab visor is lower than the roof line and trailer roof line.they end up blocking the signal when the satellite is closer to the horizon and not high in the sky
the best location for the antenna is any where it has clear view of the sky