Force 12 V-3 Vertical Dipole
This is an old photo of the antenna in it's old location when it was unpainted.
Here it is in the new location. The Dec 2002 storm bent the base section of the antenna. Still seems to work ok.
This is an interesting antenna. It is 3 vertical dipoles. The feedline connects to the center 20 meter element. From that point jumper wires connect to the 10 and 15 meter dipoles. The ends of all three dipoles are folded back at the ends to get the impedances close to 50 ohms. The feedline can be seen in the photo running down to the right, attached to that guy line. It is important to have the feedline at right angles to the dipoles to reduce interaction.
This was a late addition to the station, kind of an afterthought. After playing around with so many goofy antennas for the second radio, I learned that it was awful handy to have something with an omni directional pattern available to quickly pick up signals coming from outside the TH7's pattern.
When I first tried the antenna it did not have a very good match. I talked to the folks at Force 12 and they did not know what might be causing the problem. I noticed that the jumper wires were longer than required to reach the 10 & 15m elements. The antenna was closest to resonance at frequencies low in the bands. So, I made some shorter jumpers and that seemed to make the swr curves better in the portions of the bands I care about.
The antenna is very quiet compared to normal 1/4 wave verticals for man made noise. At first, I thought the antenna wasn't working. It does work just fine. Signals are not very loud on it compared to the beams, but that is no surprise. It is quite handy for what I wanted it to do, enable me to hear signals off the side and back of the TH7. There are many times in each DX contest where I can barely hear some peep during a run, and switching to the vertical produces a copiable signal that makes it into the log. It seems to get used the most during JA runs to pickup SA, VK, and ZL callers. I also use it sometimes in the mornings to pickup a stray Carribean/SA signal when running Europe.
This antenna is never as good as either tribander, except for the few times when the tribanders are pointed in noisy directions. It is a quiet antenna, and often I can quickly pickup a stations call with it, and work the guy, when I couldn't hear him on either tribander.