BFW
Installation Guide
AN-30e & AN-50e Systems
measuring the signal strength using a DC voltmeter. Use of either the audible
buzzer or voltage alignment pin is enabled using the software interface. A faster
the repetition rate of the buzzer indicates a stronger the signal being received from
the remote-end transmitter. Similarly, a DC voltmeter connected to the voltage
alignment pin (if equipped) will display a higher voltage when a stronger signal is
received.
5.2 Adjusting
for
RSSI
One end of the link should be aligned at a time, swinging first the elevation and
then azimuth adjustments through peaks and valleys to a maximum reading. Care
should be taken not to align on a sidelobe of the received beam, which may be
indicated by an unstable reading or a large contrast in RSSI values at each end. A
thorough elevation and azimuth sweep should see the RSSI value rise when a
sidelobe is seen, then fall and rise even further when the receiver sees the desired
signal. Further movement of the antenna will see the RSSI fall and rise to a lower
peak as another sidelobe is seen. This should be repeatable in both elevation and
azimuth at each end of the link.
Once the alignment has been completed, the RSSI value should be checked against
the estimated value obtained from the link budget. If the link is LOS, the value
should not differ by more than about five dBm. If the RSSI is much less than the
budget prediction, suspect an optical LOS or even non LOS path. The other
possibility is that the antennas are still not properly aligned and may be peaked on
a sidelobe.
When the alignment is complete, the previously loosened nuts should be tightened
while monitoring the RSSI value as a shift in value may occur. Tighten all nuts
partially using a cross-pattern to minimize any shifts in the antenna alignment.
If the link is non LOS, a suitable reflecting surface such as a building or billboard
must be used. The only certain way to determine if a non LOS link will work is to
install the link and then pan the antennas until a usable signal is received. This will
take some trial and error.
Note:
When using a magnetic compass, the tower metal will affect the accuracy.
Magnetic declination (difference between true North and Magnetic North) must
also be taken onto account.
70-00042-01-02
Proprietary Redline Communications © 2005
August
2005
Page 32 of 34
