Installation guide

MOUNTING FOR OPTIMUM SIGNAL STRENGTH
7
Antenna output signals of 500 uV and above are con-
sidered adequate. Any signal level below 1,000 uV will
require preamplification.
To use the field-strength meter, orient your test
antenna in the direction of incoming signals and
activate the meter. To orient the actual installed
antenna in an area where several channels are coming
from the same general direction, aim the antenna to
obtain the highest reading with the field-strength
meter set on the highest channel to be received.
(Channel 13 is the highest VHF channel, and 69 is the
highest UHF channel.) As a result, this will orient the
shortest antenna element as well as properly align
remaining elements. Of course, if the channels are
coming from different directions, you will have to take
separate readings for each and adjust the antenna(s)
accordingly.
ADJUSTING THE HEIGHT FOR OPTIMUM
SIGNAL STRENGTH
Just as the received signal strength varies with the
mounting site and the direction in which the antenna
is pointed (oriented), the height at which the antenna
is installed will also affect signal strength. A few feet
up or down may make a big difference in the level of
the received signal(s), especially on UHF channels.
Watch your field-strength meter as you slowly raise
and lower the test antenna.
The height at which you ultimately mount the
antenna depends on two things: signal strength and
practicality. You should mount the antenna only as
high as necessary, even if your meter indicates that
the signal level continues to increase as you raise the
antenna. Choose the height at which you get the
highest signal level without having to resort to guyed
mast and other more expensive and difficult to install
equipment. Your objective should be to get as close
as possible to an unobstructed “line of sight” between
the transmitter tower(s) and the receiving antenna so
that the signal clears all large buildings and other
obstructions.
In some cases, obtaining adequate signals may
require the installation of a multiple array. A multiple
array is two or more antennas set at different heights
on the same mast (Figure 3-2). Ideally, these antennas
should be spaced seven feet apart so that they won’t
interact with each other. If this is not practical, try to
mount them at least five feet apart. When installing
more than one antenna on a mast, try to mount the
largest (heaviest) at or near the mast support. This
will help prevent excessive strain on the mast during
high winds.
Fig. 3-2. A vertically stacked antenna array.