Kristinn:

A poorly performing vertical is usually traced to an inadequate
ground system, which reduces it's efficiency. Less often, it could
also be caused by an electrically shortened antenna, which can
experience poor efficiency. Assuming approximately one
quarter wavelength for each radial, on 40 m you would want quite a few
10 meter long radials; the plot of land needed is in the order of
310 square meters. A metal roof may or may not prove to be a useful
ground reference. There are a lot of things that can go wrong.

A 5/8 wavelength vertical achieves gain by pattern enhancement at
lower radiation angles and sacrificing signals at higher elevation
angles. If you have poor ground (in the near field) or poor ground
conductivity/dielectric constant (in the not-so-near field) you probably
will not be able to realize this gain. My experience with 5/8 wave
verticals on HF is that they did not work as well as anticipated. If the
arrival angle of the HF signal is higher than the lobe of the vertical
antenna, then 'gain' has hurt, not helped.

A properly designed 4-square vertical antenna system over a good
ground radial system will perform very well on 40 meters for DX.
The Hy-Gain Hytower vertical antenna with a good quality ground
radial system has proven to perform reasonably well on HF.

-- Tom





"Kristinn Andersen, TF3KX" wrote in message
om...
Tom: I agree with you on the 160/80m explanation for the better
performance of the vertical than the inv-V.

Generally it is assumed that polarization of arriving HF signals is
randomly oriented and constantly changing - which I have no grounds to
refute. Thus, your suggestion that my inv-V (horizontal antenna) is
simply gaining advantage from its height (and in some cases azimuthal
directivity) is a viable explanation. Keep in mind that the inv-V is
supported by an aluminum pole with an apex 6m (18ft) above my metallic
roof, and the roof itself is at 8m (24ft) above the surrounding ground
- thus the apex point is at 14m (42ft) above ground.

It just struck me that even the "supposedly best" verticals (5/8 wl,
using good connections to the metal roof as a counterpoise) are
consistently substantially weaker on reception on 40-10m than the
inv-V. The difference varies from zero to 7-8 S-units. I would have
expected the vertical to be better in at least a few cases - but it's
not.

But, OK - the inv-V dipole is gaining further from its height. Any
other suggestions, anyone?

73 - Kristinn, TF3KX


"TOM" wrote in message
news:7P%Yd.1796$oa6.1254@trnddc07...
HF signals are usually not predominantly polarized more horizontal or
vertical.

The effect that you are seeing is due to the effective height of the
dipole
above ground. On 40,20,15,10 the dipole is high enough (in terms of
wavelengths)
that it develops a good pattern at lower angles of radiation (or
reception).

On 80 and 160 meters, your dipole is too close to the ground for it to
have
a
good low-angle pattern.

Thus what you are seeing is that the signals you want to listen to are
arriving
at an angle lower than what your 80/160 meter dipoles are effective at.
The
vertical
antenna has a lower angle of reception on these bands than the dipole.

If you listen to signals out to ~300 km on 80 meters, you may find that
your
dipole
outperforms the vertical because those signals are arriving at your
antenna
from a
fairly high angle.

-- Tom



"Kristinn Andersen, TF3KX" wrote in message
om...
I have an inverted-V, approximately resonant on 40, 20, 15 and 10m.

I have tried numerous verticals for comparison, but on these bands the
inverted-V always receives signals on these bands better or equally
well, at best. The verticals have been well grounded (using a "large,
good quality" metal sheet roof as the ground) and I have done my best
to minimize losses. The verticals have been anywhere from 1/4 to 5/8
wavelengths long. But they are always outperformed by my inv-V on
these bands. Only on 80 and 160m are the verticals better.

Now, this leads me to wondering if the radio waves arriving at my QTH
tend to be largely horizontally polarized on the higher frequencies?
Or can there be any other explanation that "good" verticals, even 5/8
wavelengths long are never better than the inv-V. Any thoughts?

The verticals and the inv-V were all mounted on the metal roof of my
house. The house is located in a poor-quality ground area (rocks,
shallow vegetation), the direction to Europe is across a low hill
approx. 1/2 mile away while the direction to America is across the
open sea approx. 1/8 mile away from my house.

73 - Kristinn, TF3KX