I have been using an HR24-500 with an 18" round antenna for years. I am assuming you use the receiver for HD reception at your home, so as Bill says, the key to successful RV use is to be able to make the correct changes in the setup menu.
I use a single run of coax with no other devices in the feedline. I can only receive SD signals and can only watch/record one program at a time. This works for me.
I do carry an old SD inactivated receiver because the HR24 does not have an audible signal strength meter. I aim the antenna with the SD receiver and then change the coaxial feedline over to the HR24.