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Directional Antennas focus energy more in one direction. Here is an example of antenna gain versus vertical
and horizontal beam widths (VBW & HBW) using Parabolic antennas:
Gain vs. VBW HBW
15dBi = 17º ~ 21º
19dBi = 11º ~ 17º
24dBi = 8º ~ 10º
Getting the most out of your Wireless Network.
Under ideal conditions, increasing the gain of an antenna at one end by 6dBi should double the distance the
link will work over. Higher antenna gain means that the signal will be focused more in one direction; you do
not get more power from antenna gain, just a more focused beam of energy to give a greater distance.
Using the highest gain antenna is not always best. This is because a higher gain antenna has a narrower
focused signal beam; while it does travel further, there is a smaller ‘sweet spot’. This can make point to point
links more tricky to align and they can easily go out of alignment if the antenna mast moves slightly.
Also, with a high gain omni directional antenna the signal is focused into a narrower vertical beam width.
This can mean the areas above and below the antenna may have poor coverage. When choosing an antenna
for your system, you need to consider your surroundings first. Sometimes a 5dBi antenna will give you better
performance than a 8dBi. If your problem is due to distance in a wooden house the 8dBi is good, but if it is
due to metal and concrete blocking, the signal of the 5dBi can be better than the 8dBi. The 8dBi has a more
concentrated beam and will reflect more off the surfaces, causing multipathing problems that reduce signal
quality.
Attenuation.
The makeup of a building can affect the signal strength, things such as metal studs in walls, concrete,
concrete fibreboard walls, aluminium cladding, foil-backed insulation in the walls or under the cladding, pipes,
electrical wiring and furniture. Tinted windows will severely weaken 2.4 GHz signals also, as will wire mesh
with holes smaller than a quarter wavelength (about 2.5cm), wire mesh with holes up to 12.5cm will also
affect signal as well.
Here are some common building materials with their average attenuation:
Office window: 3dB
Plasterboard wall: 3dB
Block wall: 4dB
Glass wall with metal frame: 6dB
Metal door: 6dB
Metal door in brick wall: 12.4dB
Keep your access point as high as possible and away from metal objects and concrete walls as these can
block and/or reflect the signal causing signal degradation. If you are going between floors on a multi story
building, tilting the antenna will give you a better coverage.
Antenna Polarisation.
It is important when installing antennas that both ends have the same polarization, otherwise there will be
almost no communication between them at all. Polarisation is the relationship between the antennas physical
orientation and the electric field that is parallel to the radiating element. Omni directional antennas tend to
have vertical polarisation due to the fact that they stand vertically. Most directional antennas can be installed
in either vertical or horizontal polarisation; you just have to have the same directional antenna type at both
ends. For vertical polarisation on Intech parabolic antennas; make sure the grid is running vertically.
Good Signal Can't be Guaranteed.
Even when all the above precautions are taken into account, no one can guarantee a good link, as there are
many more factors that could cause problems. With the Z-2400 Series, an additional interposing
remote can be used in between as a repeater (particularly good when transmitting through solid walls).
Important.
Make sure you power off any wireless equipment before you connect the antenna, as you can damage the
radio transmitter if you don't. Also, all outdoor coax connections that are exposed to the weather should be
sealed with a suitable coax seal tape or the connection may become damaged over time. Many wireless
installers forget about this vital part of their installation and end up with expensive repairs a few months later.
It is very important to seal all outside connector joints to prevent moisture from entering.
Self bonding tape is supplied with all outdoor antennas.
