RickC and Nationalpatriot, IMO there are many advantages with 11 meters, being able to raise the antenna and the ground plane up high, and improved performance is probably the best of the advantages as you get above ground clutter. This is not always the case with the lower frequency antennas unless they are very short and inefficient, so ground mounting is almost a necessity in such cases. Why even mess with all the problems associated with ground mounted antennas that has a radiator that is only about 9' tall?
Using coax to make an antenna is fine and it can produce a better bandwidth than a skinny wire, but the problem is support, just like with any wire.
RickC, considerations for capacitance and velocity factors are only important regarding coax use when the current flows inside the coax, and not for current that flows on the outside---like NP suggest in his project. An antenna made with coax is just wire, and the shield is the part that your RF will flow on. I would solider the shield and the center together to add some support to the wire however. Otherwise using coax is just like wire, except in this application it is actually lighter than a comparable thickness of plain wire, and producing a wire cross section for the RF that is maybe 10 times that of a small diameter wire. This is where the added bandwidth may come from.
OK Rick, that is some good advice, considering NP wants to build an array which will be much easier than raising it up. At 11 meters however, I don't think NP could produce a ground mounted array that will perform better than even a 1/4 wave ground plane raised up 30' to 40'. Only exception might be, unless he is really out in the wide open spaces away from his house etc,. and has a radio shack out there too to cut down of feed line length.
