but it doesn’t look like the book…
last updated 28 February 2025.
Often when we put up an antenna, it doesn’t look like the drawings in the books, or even those on this website. That isn’t necessarily a problem.
It’s easy to draw a straight dipole strung between two supports, but that’s not physically possible in the real world: the weight of the wire, balun, and feedline would require infinite tension to hold it exactly horizontal. Instead, we just allow some sag to reduce the required tension. It still works just as well, and is likely to last longer before the wire (or something else) breaks.
Sometimes we have to bend our dipoles to get them to fit in the available space. Maybe the sides of a loop aren’t all equal, or it turns into more of a hexagon than a rectangle:
This rectangular loop ended up as a hexagon. It still worked.
Use whatever sticks you can find, even if they are not the same length.
The holes for the spreaders weren’t drilled straight, but it still worked.
Usually it doesn’t matter. Most simple wire antennas can tolerate a fair bit of irregularity without a noticeable change in performance. You may find that you need a bit more wire when a dipole is bent around to fit in the attic, and the SWR might not be perfect, but as long as you don’t double it back on itself too much, it should still work as a dipole. With an inverted vee, the angles of the legs don’t need to be exact (or even the same), and I’ve just tied them off to whatever supports are convenient, even if the legs aren’t opposite each other. Horizontal loops have been run around the garden / yard / house using whatever supports present themselves, even if the result shape isn’t at all regular, and the corners aren’t all the same height.
Sometimes with my portable wire dipoles I can get a rope over a branch that is much higher than my coax will reach. So I use one leg of the dipole hanging vertically to support the feedpoint, and tie the other leg off to the side to a convenient anchor. Is it a vertical dipole? sloping dipole? ground plane with one radial? It doesn’t matter – I just use it.
These yagi elements got bent while running through the forest, but it still worked.
Even a yagi beam is fairly tolerant of bent (or even missing!) elements. Sure, the gain, radiation pattern, and SWR may change, so the antenna might not be quite as ideal as the original, but often it may still be good enough to use until you have a chance to perform repairs.
how far can you go?
There are limits, however. Laying the antenna on the ground, or running it along the top of a barbed wire fence a few cm ( inches ) from the top wire, generally doesn’t work as well. So here are some guidelines to consider:
- Try to keep the center half of a dipole reasonably straight. Then you can bend the ends sideways as needed, and avoid folding them back towards the feedpoint if possible.
- With a half-wave dipole (regardless of where it is fed), maximum current (and hence maximum radiation) is in the middle of the wire, so try to keep this as high as possible. (With multiband antennas this only applies on the fundamental frequency where the antenna is 1/2 wavelength.)
- With a large loop the point opposite the feedpoint will usually have high current (although there may be other such points around the loop). It’s a good idea to make this point as high as possible in the air.
- Folding the elements back too sharply will cause a significant change in the resonant frequency. This will require more wire than the standard formulas suggest.
- Try to avoid running parallel to other metal objects for significant distances.
- More elaborate antennas (such as yagis) may suffer more change in performance than with simpler antennas if the coupling between the elements changes.
- You might need an antenna tuner.
- Do the best you can in your specific circumstances.
So don’t worry about trying to make your antenna look exactly like the drawings in the book. They are not subject to the real world constraints that we often face in setting up antennas. As you get more experience with antennas, you’ll get a better feel of what works well and what doesn’t. Don’t be afraid of having some spectacular failures useful learning experiences in the process.