Welcome, Karl:
Some of the more experienced old hands around here can give you more info, but from my perspective the FTA signals are a lot weaker than the Dish and DirecTV signals, so your 18" dish is probably not going to be big enough.
Also, as you look at Lyngsat, bear in mind that only the five digit frequency transponders (e.g., 11720) are Ku, the ones with four digits (e.g., 3980) are
C-band and will require a dish that's a wee too much for a motor home (like 8 to 10 feet in diameter).
I'm a camper myself, although with a fiberglass trailer rather than a motor home, and I've thought about toting an FTA receiver and dish with me, but the "persnickitiness" of aligning the dish
might make for a frustrating camping trip. It just isn't as easy as aligning a subscriber satellite antenna (especially if you have one of those fancy jobs with GPS and gyros and who knows what)!
I might give it a try, though, since I've gotten pretty adept at aligning my dish at home. It
would be nice to have something beyond snowy/ghosty local TV when camping (although I really don't like TV at all when I'm "roughing it", but my wife...well...)
Anybody else RV with an FTA setup?
Bob