OPTIMUM TOWER HEIGHT?
This question has been asked for decades.
The answer is that NO SINGLE HEIGHT will be optimum for ANY single
band
under ALL conditions, seasons, time of day, or sunspot activity. It is
even more
complicated when you try to cover several bands. Throw in uneven terrain
and
you further complicate the situation.
For FLAT land, two antennas at some height "H" and another at "2H" give
good
coverage. Antennas above one wavelength high with a flat foreground will
exhibit
2 or more useful lobes. Another antenna at half that height will fill in
the null
between those lobes.
Two tribanders stacked evenly on towers between 60 and 80 ft give
excellent coverage and are feasible on most city lots. Add a "shorty
forty" 2L40 on a
stout mast above the top tribander and you have a powerful combination.
Use Rohn 45 and you can safely get by with only two sets of guys.
Many computer studies have been performed to determine "optimum" angles
of radiation which support the "higher is better" theory. These models
ASSUME
equally high antennas at BOTH ends of the path.
When the MUF is much higher than the frequency in use, the ionosphere
will
support higher angles. If your target station is using a very LOW
antenna
which radiates most of it's energy at higher angles and the ionosphere
will
support those higher angles, what height do you think will receive that
signal best?
My LOW antennas (40 ft) often are stronger than my high antennas during
the day on the high bands. Most contest stations with lots of antennas
know
this. There are countless testimonials of low antennas out performing
high antennas, even from as far north as Alaska.
To paraphrase KL7RA, " You can never have enough antennas".
Practically speaking, two antennas at different heights are definitely
worth
the cost and effort and can easily be installed on a single tower.
de Tom N4KG
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