Frustration with 1/4 wave multi-band centre loaded vertical

I tried quite some designs of SOTA verticals, e.g.

  1. Interesting new SOTA Vertical Antenna - #57 by DK3IT
  2. SOTA Vertical Antenna for 40-30-20m

The key lesson learned is that it is not possible to design a tuned version that would work without a tuner in varying deployment conditions, e.g. ground characteristics, radials deployment, etc. If you have a lot of time on the summit, you may be able to tune the antenna by playing with the radials deployment, but that is annoying and not guaranteed to work.

So my next design made the Elecraft T1 tuner the center of the design:

The core idea is to do the biggest part of the compensation (for 40m, mostly), by means of a high-Q inductor at the feedpoint, and the fine-tuning by the T1 auto-tuner. This allows for fast deployment in varying environments.

The next planned iteration will replace the T1 by a simple LC match and either a Tayloe SWR indicator or the BlinkySWR. The L of the LC match will be just a bit of extra inductance on the loading coil, so I hope to need only a variable capacitor and maybe 1 - 2 switchable additional Cs in parallel for ca. 20 - 1000 pF.

But the main lesson learned is that neither a vertical nor an up-and-outer matches reliably in changing deployments. Most success stories are based on just too small a sample size ;-).

73 de Martin, DK3IT

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