Cambium Networks PTP 250, User Manual

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PTP 250 User Guide Web-based management
phn-2510_002v000 (Mar 2012) 7-11
Attribute Meaning
Link Loss The maximum, mean, minimum and latest measurements of Link
Loss (dB). See
Diagnostics calculated over time on page 7-23 .
The link loss is the total attenuation of the wireless signal
between the two point-to-point units. The link loss calculation
presented below:
L = P
T
– P
R
+ G
T
+ G
R
Where:
L = Link Loss (dB)
P
T
= Transmit power of the remote wireless unit (dBm)
P
R
= Received signal power at the local unit (dBm)
G
T
,
G
R
= Antenna gain at the remote and local units
respectively (dBi). The antenna gain of the ODU (23.5 dBi) is
used unless one or both of the units is a Connectorized
version.
For connectorized ODUs, the link loss calculation is modified to
allow for the increased antenna gains at each end of the link.
V/H Ratio The maximum, mean, minimum and latest measurements of V/H
Ratio. See
Diagnostics calculated over time on page 7-23 .
This is calculated from:
Power received by the vertical antenna input (dB) ÷
Power received by the horizontal antenna input (dB)
V/H Ratio is an aid to debugging a link. If it has a large positive or
negative value, then investigate the following potential problems:
An antenna coaxial lead may be disconnected.
When spatial diversity is employed, the antenna with the
lower value may be pointing in the wrong direction.
When a dual polar antenna is deployed, the antenna may be
directed using a side lobe rather than the main lobe.
When there is a reflection from water on the link and spatial
diversity is employed, then one expects large, slow swings in V/H
Ratio
.
This indicates the antenna system is doing exactly as
intended.
Wireless
Transmission Rate The maximum, mean, minimum and latest measurements of
Transmit Data Rate (Mbps). See
Diagnostics calculated over time
on page 7-23 .