User's Manual

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Possible Causes and Fixes
Cause What to look for / What to do
Inadequate
Receive
Signal Strength
If the link was working before, check if either of the nodes has been moved throwing off
the alignment or if something has been placed or grown into the line of site path.
Calculate required Receive Signal Strength for link distance and compare to RSSI value
reported by the node. Is the measured value close to the calculated value?
• If not check the antenna alignment, line of site path, Fresnel zone and clearance.
If everything looks good, try increasing the Transmit Power, if it is not already
set to the maximum. If the Receive Signal Strength does not increase
accordingly, you most likely have destructive multipath interference. Try
moving the customer side antenna up or down side to side to move it way from
the interfering signal.
• If it is, check that there is sufficient fade margin, typically at least 10 dB for line
of site links.
RF Interference Check for interference in your operating frequency band at both ends of the link at
various times over a period of several days. Are you using a noisy channel?
• If there is a clear channel(s), change to one.
• If there is not a clear channel utilize the RSSI Threshold feature to block out
signals below the interfering signals. If your survey finds an interfering signal of
-75 dBm, set the RSSI Threshold to -72 dBm and the Hsyteresis Window to 3.
Although this will reduce the range of the system, it will effectively block out the
interference.
• Try moving the nodes away from the interference source. Sometimes moving
the nodes just a few feet reduces the problem.
• For interference from the sides and rear, shield the radio with metal and/or RF
absorbent material.
Multipath
Interference
On very short links or links over reflective surfaces, like a body of water, (less than ½
mi.) you can experience packet loss due to bounced or multipath signals.
Multipath is most likely the problem if increasing the transmit power increases the
packet loss but not the Receive Signal Strength.
The first thing to try is to minimize the transmit power and the second would be to move
the node away from the multipath. Normally a moving the node up or down a few feet
will fix the problem. If the multipath is caused by object(s) in the Fresnel zone you will
need to relocate the nodes so the object(s) are no longer in the Fresnel zone.
Node Grounding Check that both nodes and the connection cables are grounded properly. The MetroE
node includes a lug for grounding.
Network
Equipment
Check the Ethernet network performance at both ends of the link prior to the nodes.