Can one have a TV satellite dish on a motorhome, or does re-aiming the dish every time you move make it too impractical?

King Dome makes a self-tracking dish that will lock onto the satellite automatically, and actually keep locked on even while underway (though you'd have to run the generator to power it and the tv). The biggest drawback to those is they mount on the roof, which limits the places you can park due to trees or other obstructions. Stand alone dishes take 10 or 15 minutes to set up and aim, but they can be moved into the clear for line of sight to the satellite.

I have relatives who travel with their digital satellite dish (dish network or one of the other 18" class things). It does take some time to aim the thing when setting up, but it can be done. Many RV parks provide cable access, so it is just one more thing to plug in when you hook-up.