of the DHCP server pool is the address of the device minus 100. There are 20 entries in the DHCP
server pool, thus the ending address in the pool is the beginning address plus 20. By default, the
device uses a server address of 192.168.67.1. In this case, the pool of addresses is 192.168.67.101 –
192.168.67.120. If the device address is 192.168.67.135, the pool of addresses would be
192.168.67.35 – 192.168.67.55. Any connecting devices running a DHCP client will be assigned an
address in this range. If static IP addressing is desired, assign addresses outside of the range of
the DHCP address pool (while observing the network mask).
If an IP address is supplied in the IP Address user setting, that address will be used as the DHCP
server address. The beginning address in the DHCP server pool will still be the address of the
server plus or minus 100. The ending address in the pool will be the beginning address plus 20.
6.3 RSSI
RSSI is received signal strength indication. It is a generic radio receiver technology metric used to
determine the strength of the link between a receiver and a transmitter. In the case of the NL241,
RSSI is the measurement between the NL241 and a wireless access point. The strength of this link
is recorded in dBm (power ratio in decibels) and can be found on the Wi-Fi tab in the Settings
Editor of
Device Configuration Utility
.
RSSI in the NL241 is measured in a scale between –100 dBm and 0 dBm. The higher the number
(for example, –12 dBm as compared to –72 dBm), the better the connection between Wi-Fi
devices. A reliable connection will be maintained if the RSSI reading in the NL241 stays between
–85 dBm and –15 dBm. A weak, and thus intermittent, connection will have readings between –
85 dBm and –95 dBm. For every 3 dBm increase, the NL241 is receiving twice as much signal
(radiated power). For every 3 dBm lost, the NL241 is receiving 50% less signal.
To improve your RSSI readings, shorten antenna cable lengths and use frequency-matched
antennas with higher gain. An NL241 with a 0 db gain antenna can achieve ranges of up to
32 meters (120 feet) indoors and 95 meters (300 feet) outdoors. Ranges can be improved by
installing higher gain antennas on both the NL241 and/or the wireless access point. Remember
that RSSI can also be affected by weather, vegetation, terrain, interference, and antenna cable
length and type.
6.4 Antennas
Antenna selection and placement can greatly affect the strength of the signal transmitted and
received and therefore can impact the quality of communications. The NL241 should be paired
with an antenna designed for Wi-Fi communications at 2.4 GHz (2.401 to 2.483 GHz). Ideally the
antenna will be connected directly to the NL241 or positioned in such a way as to minimize
coaxial cable length. Note that coaxial cables attenuate signals more as frequency increases; take
NL241 Wireless Network Link Interface
17
