reception for any type of 'moving' portable or fixed antenna will be susceptible to local conditions...there's nothing to be done about that... basically any blockage will cause a break in the signal, though there's typically a several second window where the receiver has already pulled in the signal info, creating a 'buffer' of time for these types of 'momentary' signal losses, so you might not really see them if they are brief, such as an overpass.
'in motion' types of satellite antennas are designed to be constantly moving and searching to acquire and stay in motion with the fixed satellite location in the sky - so as your coach moves, side to side, up or down, or in any motion, while parked or traveling, the antenna is moving it's 'eyeball' (LNB technically) to stay with the satellite...it's an amazing feat.
...most folks find that having in-motion is expensive and rarely used, while traveling... as most RVrs are parked when they turn on their TV.
I could recite, though, a couple of prime players for in-motion: Tour buses and boats.
Tour buses typically drive thru the night, after a concert, with everyone on-board either sleeping, or watching TV, or similar activities.
Boats are constantly moving, even if moored for the evening, and wanting to watch tv.
While RVs can move slightly while parked, a FIXED antenna is perfect, as it is designed to have a small window of signal acquisition that is rarely affected by that.
'14 Palazzo 33.3 bunkhouse 34' diesel
KingTailgater2 Dish HD, 100w/5a SOLAR, BlueOx
100,000+mi since '14 - US, Alaska, Canada - Hiawassee, GA! (also, '14 Gulfstream Amerilite and '07 ForestRiver Rockwood) : )