Thanks for the great info guys, I don't see myself interested in short range. DX' is what I'm really interested in. You've given me a good idea of what bands are good, and when. I will probably go for the 20 meter dipole. Quick question-I hear some people ground dipoles and some don't. Some will unplug antenna whenever away. What's the scoop on that, and where would I attach a ground wire? Thanks for putting up with my dumb questions.
Some hams do completely disconnect all their antennas when they are not in use. Some also ground their antennas when not in use. Exactly what you do may depend on your location. My area is considered "high desert" (5,500 ft altitude) and is very dry most of the time. During storms very high levels of static can build up on an antenna.
So, for example, I make sure my 5BTV vertical is always disconnected when not in use. My 5BTV is mounted at the top of a 18 foot section of 2 inch Iron Pipe. I disconnect it because a few years ago it took a lightening hit. The 80 meter resonator at the top exploded into a zillion pieces and it took out the tuner that it was plugged into. It welded all of the capacitor plates together and then came out the side of the box. Luckily, there was no other damage and the antenna still works, but only on 4 bands.
You should have a good effective ground at your transmitter. Water pipe, house electric ground, etc.. But there is no need to ground anything else on the antenna.
A dipole works against earth ground for it's impedance and radiation characteristics. A dipole that is 1/2 wavelength above earth ground will exhibit a feed impedance of around 72 Ohms. 1/2 wavelength is also the optimum height for good low angle radiation. Low angle radiation is necessary for good DX.
As you raise it or lower the antenna, from the 1/2 wavelength point, the feed impedance will change. You can lower the antenna to get a pretty nice 50 Ohm input impedance. But at the same time you change the effective radiation angle. The modified radiation angle may effect your ability to work DX.
If you get low enough, you get into a region known as NVIS (Near Vertical Incidence Skywave) where your radiation is going mostly straight up. This isn't good for DX but is great for local operation. When I first started in amateur radio, this was just known as a crummy antenna. But over the years they gave it a name.
You should get a copy of the ARRL Antenna handbook. All this information is in the book. New, they are pretty pricey but you can usually pick up a older edition at a ham fest for cheap. They change very little, from year to year, so old copies are just as good as new ones.
Martin - K7MEM