[TowerTalk] How Helically Wound Verticals Really Work (was : Vertical dipoles)

[Dan Zimmerman N3OX]

>
> Anytime a model produces results that are not borne out by the group
> experience of those of us practicing THE ART OF THE ANTENNA, it makes the
> model results suspect until definitely proven otherwise...
>

On the group's average 0.5dB accuracy measurement range???  :-)

G3TXQ says:

>Once I include wire losses and add a Q=400 base loading coil for the
> straight vertical, the total losses appear to be within 1dB of each
> other, with the helical having the edge.

I don't see anything in there that is a reason for implicit mistrust of the
model.  A helical is better than a high Q base loaded vertical.  Helical
winding is worse  than a lumped mid-loaded antenna.    Doesn't seem
particularly strange to me.  It's somewhere in between.  The effective coil
height *IS* higher than with base loading, so you get a more favorable
current distribution.    It's non-optimum in terms of wire length (and hence
loss) but there's no reason to assume it's going to be worse than ***all***
possible lumped loading coils in various locations.

Steve, what's the current distribution look like on your helical model?
Does it peak at the base or higher up?  Just curious.

73
Dan