Codan Radio Radio Repeater Systems Training Guide - Manual (Page 36)

TRAINING GUIDE | RADIO REPEATER SYSTEM
Chapter 3: Repeater System Equipment Page 28
ACCOMMODATION
Before discussing buildings and antenna mounts, it should be noted that the repeater and duplexer(s)
are often mounted in an enclosed water and dust resistant housing on a standard rack. When
calculating rack space requirements, note that one standard rack space equals 4.44 cm (1 3/4 inches).
In the interest of neatness and ease of maintenance, shelves of one type or another should also be
constructed for your batteries.
Buildings of all types from plywood and pre-fab units through brick, concrete and metal, to those
constructed from fi berglass have been used to house repeaters. Your choice depends on weather
conditions at your proposed site and the space required. Repeater systems in areas where high winds,
heavy snow levels and / or heavy icing is prevalent are the most diffi cult to house. Consider the
following:
i) square buildings ice up easily at the corners, and may be diffi cult to fi nd in deep snow;
ii) in deep snow, cylindrical buildings have proved most satisfactory as wind action “scours out” the
snow around the circumference;
iii) expect condensation in metal buildings in most high locations;
iv) treated wooden poles are superior to light metal towers up to 15 meters (50 ft.) in height. Allow
0.3 meters (1 foot) in the ground for each 3 meters (10 feet) above ground. Do not concrete a
pole into the ground;
v) marmots, porcupines and wolverine will nest in your building if they can enter. In areas where
they are known, use construction material other than wood;
vi) vandals have been known to winch down fences and gates, power saw through walls and shoot
off locks. Concrete construction and steel doors may deter them;
vii) the building must be large enough to hold the equipment and usually the power supply. It is
also an advantage if the antennas can be inside, as under these conditions, light duty (and less
expensive) antennas can be used. In this case, high winds and icing are no longer a factor;
viii) outside antennas and solar panel mounts must be robust enough to withstand high winds and
icing conditions whether mounted on a pole or a heavy duty tower;
ix) ideally the building door is situated to the south (to allow natural light inside), away from the
prevailing winds (where ice and snow will congregate and require more effort to clear for
maintenance) and visible from road, trail or helicopter landing (for safety and ease of access),
and;
x) when your site is below timber line, unless on a bald knob with a “good take-off” in all directions,
a tower, high enough so that the antennas will be in the clear, will probably be required. A self-
supporting tower is recommended. The accommodation for your equipment and batteries can
then be of any convenient type.
Figure 3-5 shows different building types under varying conditions. Particularly note the cylindrical
fi berglass housing.