User's Manual
Antenna Evaluation
February 2004 19
Basically, higher gain antennas concentrate more of the available RF energy into a smaller, more focused
beam. The total amount of energy radiated from each antenna is therefore approximately the same
(assuming that each is equally matched to 50 ohms).
3.3.3 Tilt Angle (Down Tilt)
Figure 7 shows an antenna with a narrow vertical pattern. Because of this pattern, when you use this type
antenna in an open pit mine, you must verify that it provides radio coverage in all areas where you need it.
For example, the left side of Figure 8 shows an access point that is providing coverage to the upper
portion of a pit. Any equipment traveling in that part of the pit can communicate with the access point,
but vehicles near the bottom of the pit will not have reliable radio contact.
The access point on the right side of Figure 8 has its antenna tilted downward. Now equipment near the
bottom of the pit will have an improved signal, but equipment in the upper portion of the pit will have
poor coverage.
Level Antenna Antenna with Down Tilt
Figure 8 Antenna Tilt Angle (Down Tilt)
To change an antenna’s tilt angle, adjust the antenna mounting hardware or alter the antenna’s mounting
position.
Note: For antennas mounted on mobile access points, you can change the tilt of
the antenna by adjusting the vertical height of the outriggers on the trailer.
3.3.3.1 Vertical Coverage by Antenna Type
Certain antenna types are more suitable for covering areas with large vertical elevations.
Parabolic
antennas
Parabolic antennas increase gain at the expense of beamwidth - they
have a narrow horizontal pattern and a narrow vertical pattern. (may
have limited usefulness in the situation shown in Figure 8)
Omnidirectional
antennas
Omnidirectional antennas (“omnis”) have a 360 degree horizontal
pattern, but some have a narrow vertical beamwidth. (may have
limited usefulness in the situation shown in Figure 8)
Sector antennas
Sector antennas have a smaller horizontal coverage pattern than
omnis but provide better vertical coverage and higher gain.