The closed panel type antennas like the one at Costco and the dome type antennas like the Winegard and others are overpriced for the performance. The antennas that are a panel or small dome, or a small cylinder, do not work very well. The antennas that are at least 2' long and have the elements sticking out and look like an old rooftop TV antenna in miniature usually work pretty well. (Note: The bigger and uglier a TV antenna is, the better it usually works--of course, big is not usually workable for a camper)
One of my hobbies is TV DX'ing--that is trying to receive distant TV stations--and I'm always trying all sorts of TV antennas from a length of wire up to a giant Yagi. We traveled from the Northeast , to Florida, and out to Texas and back this Feb & March and I checked TV reception at each stop.
The cheapest and best, but limited, performance for the money is the simple pair of rabbit ears (use Velcro to mount it inside the camper) ---$3-$12. And sometimes you can find them at a closeout or even a dollar store. they are only good for indoors, but will pick up many channels IF you are close to a major city--that is within 10-15 miles. I picked up 30-40 stations at various spots within 30 miles Orlando, Florida (Titusville, Tavares, and Turkey Lake campground) with rabbit ears on the inside of the Eggcamper
. But when we stayed one place in Ocala, Florida, just 70 miles north--we got Zero stations. i got 15 stations about 20 miles west of San Antonio, TX. The closed panel antennas won't work much better than the rabbit ears--even if they are amplified. If the closed panel antenna is mounted outside it will probably do a little bit better. In the end, the rabbit ears work just about as good as many of those fancy $100 antennas.
But the next antenna will work much better for a lot less money.
Here's a couple of outside yagi TV antennas in the $25-$60 price range that work well:
HDTV Rotor Remote Outdoor Amplified Antenna 360° UHF/VHF/FM HD TV 150 Miles - Walmart.com
Amazon.com: Customer Reviews: ZENITH VN1ANRA28UL Outdoor Active Rotating Antenna with Remote
These both are the smaller,(only about 2 ft long & 18" wide) modern, digital version of the standard TV rooftop antenna. I've put one on an extendable paint
pole ($15 at Walmart) and run the cable inside. They are not fancy or even very high quality antennas, but they work well. You may find the rotor function hard to work, and it's often easier to just step out and rotate the paint
pole by hand until you get the most stations.
A third option is a small Yagi antenna similar to the 2 antennas above, but no rotor or amplifier. You can probably buy a small yagi style TV antenna at radio Shack,if you can find one that is still in business. The antenna I use is very similar but actually a Ham Radio antenna:
Yagi antenna, 2m/70cm, 3+5 element
It's light--I mounted it on the paintpole and turned it by hand, and I use it for both TV reception and Ham Radio VHF-UHF Transmit/Receive.
When we were at Hunting Island, SC, we got stations from both Charleston SC and Savannah GA--all the major networks & PBS. And Hunting Island is about 40 air miles from Charleston & 35 from Savannah.
No need to spend a lot for a TV antenna. I can not find an antenna that works better than the TV Yagi costing $25-$60. The TV Yagi and the Ham Radio Yagi's should have similar performance, and the amplified TV antenna will be the best choice for most folks for an outside camper antenna that is reasonable size, and works well. If you really like TV while camping, and want the best reception, pick the highest elevation campsite you can.
If you are more than 30 or 40 miles from a major city, you may not get any or just a couple of TV stations no matter how much $$$ is spent on an antenna or antenna system. And, if more than 50 or 60 miles from TV stations you can pretty much count on No reception at all. Then, Direct TV, or similar, would be needed.