The adjustable vertical that someone mentioned is the StepIR. They have two sizes, one covers through 40 meters, the other through 80, with an add on for 160. Because it is tuned to resonance on a specific frequency by the motor at its base, it does not require a tuner.

As was said, however, they are expensive. And, they do require radials.
The only vertical which would not require radials would be one that is a half wave length for a given band.

That is due to the properties of a half wave length antenna, AKA dipole.

The maximum current point of a half wave is at the center. This is part of the principle behind most of the Gap antenna models.

For a quarter wave vertical, the radials form the other half of what would otherwise be a dipole, or a half wave vertical. Thus, if that quarter wave is ground mounted, the maximum current is at ground level, or at roof level if the antenna is mounted on the roof.

The only differences between the S9 43 foot vertical and those from O5 or DX Engineering are the price tag, and the mechanical strength. Side by side, you would not be able to tell one from the other in terms of performance. But remember, all 3 of them would require both a tuner and radials in order to function on any frequency.





Mike Duke, K5XU
American Council of Blind Radio Amateurs