Antenna Specialists made an antenna called the super colinear for a short while. It was a 5/8 over a 1/4 wave design for 11 meters. It did not sell well because it was so large. But it was by far the best omni antenna made for CB. Several people I know made 11 meter extended double zepp antennas, and hung them vertically out of tall trees. A friend of mine here in Tampa has a vertical dipole hung from the tallest limb of a pine tree, and it works very well for him on 10/11 meters.