Afar AR24027, Руководство оператора

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AR24027 Operator’s Manual
3-8
In most installations you may want to change several other parameters. The table below shows the
most common ones and the associated commands to change them. Refer to section 4 for a complete
description of each command.
Parameter Description Command
RF channel You may need to change the RF channels if there is interference
on the default channel (20). You can configure the RF transmit
channel independently from the RF receive channel. Refer to
section 3.2.7 for the procedure for choosing new channels. rf-receive
rf-transmit
RF transmit
power The factory default is 18 dBm. You can configure this parameter
in 1 dB increments from 0 to 23 dBm. Take care not to exceed
the maximum power limits as described in sections 3.2.8 or 3.2.9 rf-transmit
Network ID The default value is 0. Change this value in all radios to a unique
number to avoid unauthorized radios from joining the network
node
3.2.7 Spectrum Analysis and channel selection
Radio operation in unlicensed bands has the potential of suffering from interference from other
equipment operating in the same band. The use of directive antennas greatly reduces the potential for
interference. In addition, the
AR24027 includes several features, described below, to identify and
overcome sources of interference.
The AR24027 can be commanded to perform a spectrum analysis of the ISM band and report the
results in either a graphical or tabular form. The command:
> spectrum-analysis input=a-antenna dwell=xx
instructs the radio to scan the entire band, dwelling on each channel for a programmable amount of
time, and record the highest signal level in that channel. This feature can be used to perform a site
survey and identify the best receive channel.
Note that even though the AR24027 channels are spaced 2 MHz apart, the receiver RF bandwidth is
approximately 5 MHz. Therefore the RSSI value reported for each channel represents the total
energy in a 5 MHz band centered around that channel. For this reason, a narrow band transmitter will
show up in the spectrum analysis report as a lobe with 5 MHz bandwidth. Conversely, you do not
need to find a quiet 5 MHz wide region in the spectrum analysis report to select a quiet channel, i.e.,
any single channel sample that shows a low “noise” level, is a good candidate to select as a receive
channel.
Once a potential receive channel has been identified using the spectrum analysis tool, a “timing
analysis” may also be used to confirm that the selected channel is indeed clear. The command:
>time-analysis channel=xx input=a-antenna dwell=xx