I haven't been on the site for a while, but about 8 years ago I built what might have been a one of a kind, and ordered 8 3" magnets, and mylar coverings from Hustler down in Texas, and built a crossbar network using 1" flat stock 1/4" thick aluminum; I run a Swan 45 in the middle, and 4 other smaller antennas off to the sides.......the only hf band that I operate on at night is 75 meters, and 40 in the daytime.

The best compliment I was ever paid was on 75 one night while a few miles south of the grapevine a friend of mine asked me what I was up to and I told him that I was going to a ham swap in Livermore, and he exclaimed "you mean that you're mobile, I thought you were at home on your base".  I run a single 4-1000 amp at home, and I was running 100 watts out of my Icom 706 at the time he said that.

One of the things that I did was that I didn't rely soley on the capacitive contact to the roof, I ran 4 1" flat silver braid strips from the mount to the inside the door posts of my 96 Impala, exactly the same way I did on my 89 Caprice; now the same setup is about to go up on the roof of my 2001 Suburban, and for the first time ever the Swan is going to get a kw run through it, which shouldn't be a problem its rated for 2kw pep.

So, the point of my response is don't believe people who say you can't work the lower bands mobile......I have a friend who's been working 160 mobile longer than the 21 years I've been a ham.

Another well kept secret to my setup is that I don't use a tuner or an inductor, but a single 500pf 15kv doorknob (lpn type)cap shunted at the base...it gives me a 1.5 to 1 on 75, and a 1.2 to 1 on 40; if I worked higher freqs I'd have to unscrew it....that takes about 5 seconds.  I am a total believer in shunt grounding because it works extremely well, and even though lossy inductors are much more popular; I personally could care less what is popular.  73 and good luck on your mobiling endeavors.

If you can attach a vertical support component to the dock, i.e. a long fiberglass or wooden pole then you've got your starting point, and if you use heavy wire like 10 gauge stranded, that should act as the additional guying support for the vertical's stability, and then you'll need two more supports for the ends.  

If your dock is not particularly strong you might consider a weighted support on the ocean floor under the dock for the vertical mast, and then use a sliding coupler attached to the side of the dock if you have the type that floats up and down with the tide changes.......if not, then just make a permanent attachment dockside, and you've already got two support points secured before you string the wires out to the sides which will give you the 3rd and 4th supports.  The downside is that remember that when you use a larger wire size, the sag of the wire will increase, and the point is: that the higher your vertical supports are the better off you will be.  However, the only one that is crucial is the center support because you can always direct the ends downward in an inverted v configuration, which will probably be an advantage to you anyway because most of the guys working 160 are more vertically oriented than horizontal.  So if you do it that way your two end supports won't have to be very long at all, which means that guying them will be much easier.......you might even be able to just dig a hole in the sand for each of them and use some quick set concrete as their bases.  73's and good luck, Ron      kd6od@netzero.com

The first thing you need to consider is what power level it will comfortably handle.......some baluns will handle 1kw, but if you run 1500 watts to them you'll fry them.  Another main consideration is what kind of a feed you're going to use; if you're using 50 or 72 ohm coax to an inverted v or a dipole you'll want a 1 to 1 type; if its a ladder line feed like 300 or 450 ohms you need a 6 to 1 or a 9 to 1 type.  Additionally, you have current baluns, and you have the voltage type, I don't recommend the latter.  Over the years I've seen some excellent articles on baluns in some of the ham mags, and I think the arrl handbook has a pretty good section on them too.  73's  Ron kd6od@netzero.com