Tuesday, January 2, 2018

End-of-the-dipole DXing

RI1ANO (op Alex UA1OJL) on South Shetland Island was so strong on 80 meter CW a few nights ago that I could copy him on my tribander. Switching to the dipole made him an honest 589 and two quick calls put him into the logbook. It was too easy and I thought I might have worked a pirate until Alex updated his online log.

Bouvet is only 20 degrees in azimuth from RI1ANO relative to my QTH. Both are off the end of my dipole so I don't know what accounts for RI1ANO's strong signal but I'm starting to think that working Bouvet won't be such a tough task after all.

DXing via FT8 on the first day of 2018 resulted in another off-the-end (the other end) of-the-dipole entity - 4S7AB on 40 meters.

The dipole for both contacts is cut for 80 meters, fed with ladder line for multi-band operation and is 90 feet high. It has minimal radiation off the ends on both 40 and 80 meters.

As Forest Gump might say, "Sometimes this radio stuff just don't make no sense."
That's all I have to say about that.


  1. Even at 90 ft, you're only about 0.32 wavelengths above ground on 80 m, so there should be considerably radiation at higher angles above the horizon in the directions of the ends of a half-wave dipole on 80. Now on 40 it's another story.

    David, VE7EZM and AF7BZ

  2. Good morning David. I forgot to take into account that the ends of each leg of the dipole are bent downward to accommodate the spacing between the trees that support them. I suppose I should model it with that characteristic to see just how non-directional it is on those two bands. 73 and HNY.

    1. What I said holds if the dipole is horizontal. It holds even more if the ends are dropped as you describe. From the point of view of an observer broadside to the antenna, at any vertical angle, those two vertical portions are out of phase so there is cancellation; in other words in such directions there will be less radiation than if the dipole were horizontal. But from the point of view of an observer off either end of the antenna, at any vertical angle, the fact that current is going upward in one wire at the same moment it is going downward in the other makes these two segments behave like an end-fire array with gain in those directions.

      If you do model it, model it twice, once with the wire horizontal, and once with it the way it really is. Numbers for gain at various elevation angles and in different directions would be interesting to see, but I'd be very surprised if what you find doesn't confirm my predictions.

      72, HNY, and good DX to you on 80!

      David, VE7EZM and AF7BZ