from the research i did on whether or not to buy the gear for the RV.
OUCH its $$$$$$$, anywheres from 3 -5 k for a mobile system on the roof and 700-1500 for a pole tripod portable system, this was of course not inlcuding a monthly connect fee of 49-69 buckaroos per month, but if i made my living that required an online connection 24/7 if would be nice, but...
the tripods may be an exstinct animal soon as the fcc is looking to enforce some restrictions on mobile set ups, like it has to be XX feet off the ground, and cant be pointed at certain angles so your not zapping people with a low energy beam

etc.
you start putting an antenna thats almost a meter across and weighs close to 40 lbs 6-8 feet off the ground on a tripod and you need some serious tie downs....
the one that mounts to the roof of the rv is

but its very $$$
a home station is less expensive 700-1500 for gear and such,
best thing is you need no land line to establish a connection
but the speeds available are fantastic
click here