For the caravan I was looking for a simple not to big dual band antenna for 2m and 70cm. And the materials should not be difficult to get. I found this design on internet. The original design is from DL4KCJ en is used at the DARES (Dutch Amateur Radio Emergency Serves). It's called the Popovic-antenna. The antenna is a quarter wave for 2m and a 5/6 for 70cm. I made this antenna with different materials and works great. The SWR on both bands is below 1:1.2.
I want to use materials which you can buy with the do-it-self store. The only thing I bought at a radio market is the plastic cabinets. The pictures below show more than words can say. It's an easy to make antenna and an easy to transport and setup.
Orginal DARES dualband (PDF)  (Dutch)