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Limitless™ WDRR Receiver
8.4.2 Outdoor Antenna Installations - Lightning Concerns
Outdoor antenna installations can lead to the possible damage caused by nearby lightning strikes that induce
charges or surges on the antenna and/or antenna extension cables.
A lightning arrestor such as the AL-NFNFB-9 from Hyperlink Technologies can be reviewed against application
requirements.
ATTENTION
National, local, and/or regulatory agencies may require the use of a lightning arrestor and possibly
other requirements for an antenna system installation. It is recommended that the customer review
and adhere to these requirements.
8.4.3 RF Interference
The Limitless™ input and WDRR radio operate in the 2.4 GHz range. Upon initial power-up of the WDRR radio, it
will automatically scan each of the 12 channels in the 2.4 GHz range and choose a channel with the least amount
of usage energy. This provides a level of protection from RF interference as the chosen channel (where RF
communication is low) will have a lower chance of signal collision.
However, if multiple RF sources exist in the chosen channel, the external source has extremely high power
intensity, or it is in close proximity to the Limitless™ Series antenna, RF interference can cause an RF signal to not
reach the Limitless™ input or WDRR. RF interference can be caused by many sources (i.e., other radios in the
same operating range, high frequency digital products, conventional microwave ovens, etc.). If the Limitless™
Series is in an environment with a high usage of products in the 2.4 GHz range, or the RF environment is unknown,
an on-site RF survey may prove to be valuable in identifying possible RF interference sources along with other
existing wireless devices.
Once the RF sources are identified and located, it may allow the Limitless™ Series antennas to be moved away
from the identified RF sources to achieve acceptable performance. The other option is removing the external
source, if feasible.
8.5 Choosing an Antenna Gain (dBi) with Acceptable Fade-Margin
There are several different Limitless™ Series antenna gain options to choose from. This section helps determine
the antenna version(s) that will provide suitable RF signal performance for specific applications.
The Limitless™ Series antenna's actual gain is measured by how much of the input power from the WDRR's
internal radio is concentrated in a particular direction. The WDRR antenna transmits RF signals, and also receives
RF signals from a Limitless™ input. In a particular application, transmit signal strength may be better than the
receive signal strength or vice versa. The intent is to choose an antenna with the optimum gain relative to
application conditions for both transmitting and receiving.
Fade-margin is the amount of excess power available above and beyond what is necessary to maintain a reliable
RF signal between the transmitter and receiver. Normally, an acceptable threshold of excess power to ensure
effective operation in a variety of environmental conditions is 10 dB. A simple way to determine if the signal
strength is sufficient is to temporarily install a 10 dB attenuator* between the RP-SMA plug of the antenna or
remote cable and WDRR's RP-SMA jack. This should be completed in an operating application environment with
good nominal environmental conditions. Starting with the antenna chosen in Section 3 & 8.3, install the attenuator
and operate the system until exposure of all normal application conditions is completed while monitoring the Lost
RF LED and/or Lost RF Signal Output. If the fade-margin is unacceptable, the Lost RF LED illuminates solid (lost
RF signal output changes state) indicating the antenna position on the Limitless™ switch and/or WDRR receiver
will need to be changed and/or another antenna type should be chosen. The RF Signal LEDs are also useful in
indicating the RF Link Strength; refer to Section 5.5 for more information.
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