[Elecraft] Verticals

[Ron D' Eau Claire]

Jason wrote:

> Anyways, on to my point... I wanted to know what kind of
> performance you can
> get with a vertical.

Verticals work GREAT! Marconi spanned the Atlantic with one.

Comparing a simple vertical with a simple horizontal antenna there are two
significant issues. Who do you want to reach, and how high can you put the
horizontal?

If your over-riding concern is to have the most uniform low angle radiation
pattern with no directivity, the vertical is the best choice if it is
installed "in the clear" where there are no nearby objects to interfere with
its pattern.

If you want maximum signal for DX and can get the horizontal up 0.3
wavelengths or more above the ground, the horizontal will significantly
out-perform the vertical. The horizontal interacts with the ground to
produce "gain" in its major lobes when it is high enough. It will show some
directivity (although, contrary to some beliefs, it is never zero in any
direction in a real antenna).

But if you cannot get the horizontal up that high (about 40 feet on 40
meters or 80 feet on 80 meters) the vertical usually will do a better job.
That's why verticals are so popular on 80 and 160 meters and pretty common
on 40: many of us cannot get a horizontal up far enough on those band to get
any advantage over a vertical. Indeed, if the horizontal is low enough, a
vertical will outperform it with low angle radiation.

If you want to work short skip and locals (beyond a few miles) a horizontal
will usually do much better. A vertical has less radiation at high angles
than a horizontal. The higher angle radiation from the horizontal produces
stronger short-skip and local signals. That's why some ops who like to work
short skip purposely install a horizontal antenna at a low height. They are
called "cloud warmers" and produce very consistent and strong short skip
signals.

It's hard to beat a vertical for its relatively small "footprint" and ease
of installation, and it's hard to beat the extra gain of a horizontal at a
decent height (approaching 1/2 wavelength) and its higher angle coverage for
short skip contacts. It depends upon how much space and energy you want to
put into your antenna.

Both vertical and horizontal antennas suffer when they are made short.
Either one will work quite well when they are only about 1/4 wavelength
long, but the efficiency drops very quickly once the length goes below 1/4
wavelength. Furthermore, an "end fed" antenna (such as many verticals), 1/4
wavelength long or less, suffers from the need for a good low-impedance r-f
ground - either an extensive ground system or a good tuned counterpoise.
Without it, the pattern of the vertical remains the same but the efficiency
drops dramatically. That's why the popularity of the GAP and other so-called
"half wave" verticals. And while the manufacturers have done a good job
designing a "low loss" means of "loading" a physically short antenna to
look, electrically, like it is longer than it really is. Even so, it is
still less efficient than a 'full size' antenna. So if someone says that an
antenna is a 'full half wave long' on 40 meters, it'd better be 66 feet end
to end or it's not a "full half wave long". It might work well. It might
even work nearly as well as a real half wave antenna (or not), but it won't
work as well as a full sized antenna. All "loading" schemes involve some
losses.

The same applies to shortened horizontal antennas.

Finally, there is an important point you touched upon. You have lots of
homes around you with aluminum siding, and you have trees. One cardinal rule
is for the antenna to be 'in the clear' for best efficiency and to be able
to predict the pattern and performance. At the lower frequencies, trees and
buildings will have a much smaller effect on the performance. The length of
the radio wave is what determines their effect. As the wavelength gets
longer, the relative 'size' of the trees and buildings gets smaller in terms
of wavelengths, and their effect is reduced. So at the higher frequencies,
the buildings and trees will reflect and absorb a lot more energy. Also, if
there are conductors (like your tree, perhaps) quite close to your antenna,
the currents in the antenna can induce currents in the conductor. That
energy is lost as heat. That effect increases as the frequency is decreased.
("Lowfer's" operating down on the VLF range avoid trees like the plague,
from what I read).

Some ops, like Jerry Sevic, W2FMI, who had a open piece of land several
hundred feet on a side, built a 6-foot tall vertical for 40 meters with an
extensive grounding system and found its performance virtually identical to
a full-size vertical. But that's without significant obstructions close in.
And he was comparing it to a full size vertical, not to a horizontal at an
effective height above ground.

If you've got metal buildings or other obstructions, vertical or horizontal,
you will be better off to get the antenna up and "in the clear".

Ron AC7AC
K2 # 1289