One would be surprised what a single driven element made for 20 15 and 10 
or, the one I had, was for 30 17 and 12 meters.  Something like that is 
light enough to put on a low mast with a light weight rotator, too.  People 
think you have to have tall towers and big antennas to have maximum fun on 
the air working DX but believe me, when limited room and limited funds is an 
issue, a rotary trapped dipole works amazingly well at even 25 feet.  An 
amplifier of just 400 to 500 watts makes a big difference, too, compared to 
running 100 watts barefoot.  Working more CW nets better results when 
running 100 watts.  Sure, multiple elements means front to back and a 
heavier rotor but it also means you are turning the thing many times more 
than with a single element.  One of the best 2 element tribanders ever made 
was the Hy Gain TH2 which I ran for years.  With single driven tri band 
trapped elements on a shorter mast, you can rotate it from the ground, if it 
is bolted to the house at about 12 to 14 feet that is, and you only have to 
tap the rotator for a short time to swing broadside.  Why not just put up 
wires, you ask?  Sure, that's fine but give me a horizontal rotating antenna 
with a single driven element at 25 feet any day over an inverted vee at 40 
feet.

Phil.
K0NX