Since I reconnected the coax to it, my vertical dipole – a tribander driven element hung from a high tree branch – has still not seemed to work well. I would switch back and forth between it and my 20/40/80 horizontal fan dipole, and the horizontal was always at least an S-unit better. In the WPX SSB contest the vertical dipole was only better when the signal came from directly off the end of the horizontal dipole, and I began to think I had water in the coax.
Late that Saturday afternoon, though, as I kept switching between antennas, I noticed the vertical was just about equal with the otherwise-always superior horizontal antenna, and a little later I noticed the vertical was _better_! As the sun sank low in the March sky the vertical began outperforming the horizontal dipole by a full S-unit, and I made a lot of Qs with it. For a more than two hours I used it almost exclusively. I was flabbergasted (but pleased). This was an antenna I had thought most certainly had a problem, but it was now my best one.
It was a real lesson to me – the difference had to be the radiation angle. The vertical dipole puts all its energy (and reception efficiency) close to the horizon, while the horizontal dipole casts a lot of radiation much higher into the sky. Maybe it has been due to the extremely low solar activity, but the high angles must have been predominating on 20 meters for many months, with the low angles only being favored when the band was stretching out late in the day, radiation angles were decreasing, and high angle signals were no longer prevalent.
This is why I _always_ prefer to have two antennas for any HF band – one vertical and one horizontal. There are good reasons to expect high angle signals to prevail at certain times and low angle signals to prevail at others, and having the choice makes my station work ever so much better. I am also glad to know I don’t have to lower and fix the vertical dipole (again).
Best rx & 73 de kt8k – Tim
Addendum November 2009: As it turned out, performance of the vertical dipole continued to degrade until I finally took it down and disassembled the traps. In one trap was a sizeable colony of ants, probably only slightly warmed by my QRP power, and in another trap was a really amazing collection of spider nests and webs. Once those were cleaned out and the antenna put back up it worked considerably better. Note that ants will use anything as a highway, and the ropes and the dipole itself were giving them a straight path to import supplies from the ground up to the 60+ foot level in the trees. Some of them decided quite rightly that the hollow trap tubes made a great place to set up a nest. I once saw ants going up the side of my house and traced them up to the phone line, which they followed all the way (80 feet or more) to the pole at the back corner of the lot, where they descended to their nest. They used that “highway” to haul all kinds of ant-freight that whole summer. 73 de kt8k – Tim