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Optimal Antenna Configuration
A variety of antenna types can be used with the M-2911. The antennas available from Beckwith Electric are
FCC qualified for use with our product. Use of an antenna not supplied by Beckwith Electric could violate
FCC licensing and result in fines to the user. The antenna supplied with the unit is an omnidirectional
antenna. An omnidirectional antenna is so named because it is designed to radiate equally in all directions
horizontal to the antenna. These antennas have been designed to radiate in a horizontal pattern, which is
best approximated by a toroid, or "doughnut" illustrated in Figure 7. This is also why most omnidirectional
antennas are rated to have a three dB gain over a true spherical radiator. The antenna appears to have a
power gain of two times (3 dB), compared to a true spherical radiator.
Optimum performance of Beckwith Electric-supplied antennas is obtained when the main axis of the antenna
is located perpendicular to the Earth's surface. This allows the toroidal pattern to radiate the maximum range
in each dimension. When the RF energy of the radiation pattern contacts ground, or a grounded surface, it is
absorbed in varying degrees depending on the conductivity of the surface. It is important to have a clear
view, or "line-of-sight" between antennas as illustrated in Figure 8. Any obstructions between the antennas
can absorb some energy, and can reduce the range of operation. Also, if a grounded plane is located parallel
to and close to the antenna, such as a wall located next to the antenna, it can change the impedance match
between the antenna and free-space. This condition can severely reduce the range that can be normally
obtained in unblocked directions. A rule of thumb is to ensure that any grounded objects are kept at least 10
wavelengths (50 inches for 2.4 GHz) away from the antenna in the plane of radiation (Figure 8). 50 inches is
only a guideline, and may be shortened if extreme range is not required. Some experimentation with antenna
location will be needed to optimally set up wireless in a substation environment.
The following should be considered when planning a wireless project:
1.
The resonant frequency of the water molecule is within the 2.4 GHz band, which can cause a
reduction in range during rainy weather.
2.
Trees (especially pine trees) can have >80% water content, and as such can be a barrier to
wireless signals. As long as antennas have a direct line of sight, trees should not cause a
problem.
3.
Proximity of the wireless project to cell towers, 2.4 GHz telephones, WiFi access points, or
Bluetooth wireless devices.
If you are experiencing difficulty communicating through the M-2911s, ensure that the antennas are:
•
In direct line of sight with each other.
•
Oriented vertically with respect to earth.
•
Within 1500 Ft.
You may be encountering interference from another source. Some examples of interference are
cell towers, 2.4 GHz telephones, WiFi access points, or Bluetooth wireless devices. If the
interference cannot be compensated for by relocating the antennas or reducing the distance
between them, then other antenna types may be necessary. Please contact Beckwith Electric if
you would like to discuss other antenna options.
M-2911 BlueJay Wireless Data Transceiver
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