8A535X03 Rev. Preliminary-00
Page 14 of 17
IMPORTANT
The OCR Power Output and CAS Thresholds determine the OCR maximum Gain,
which must be at least 10dB lower than the measured overall system isolation. The
isolation measurement and gain setting procedure is described in the
Setting up the
OCR Gain
section of this document.
SETTING UP THE OCR MAXIMUM GAIN
The OCR has the receive and the transmit frequencies the same. The Gain range is 70 to 140dB in
OCR mode. However, the gain is limited by the isolation that can be achieved between the rest of
the RF system i.e. cables, antennas, filtering etc. The maximum Gain setting must be at least 10 dB
lower than the measured overall isolation in order to prevent OCR lock up.
Once the OCR is programmed, installed and connected to the rest of the antenna system, the
Maintenance
screen can be used for measuring the isolation and setting up the gain as described
below. No extra test equipment is required.
Open the
Maintenance
screen from the
OCR Setup
pull down menu. The Maintenance screen is
not a programming screen. It is used for diagnostic and setup only. The fields seen on the
Maintenance screen are described in the previous sections with the exception of the measured data
fields shown on the right hand side and marked with “?”.
DOWNLINK MAXIMUM GAIN SETTING:
Ensure that the correct channel is selected (if the OCR is programmed with more than one
channel in the
Channel Data
list).
Set the desired maximum power output in the
Power Setup
field.
Make sure the donor site is not transmitting by observing the
?CM CAS
fields (should be
Idle
when no carrier is present).
Key up the OCR by setting
PTT
to ON.
Read the “own”
?RSSI
level from the
Maintenance
screen
The difference between the Tx power setting and the received “own” RSSI is the Antenna /
system isolation.
Unkey the OCR by setting
PTT
to
OFF.
Key up the Donor site and read the donor ?RSSI level off the Maintenance screen.
Set
the
RSSI CAS Threshold
to at least 10 dB higher than the measured “own” RSSI level and
6dB lower (better) than the measured Donor RSSI. If the above is not possible, the power output
needs to be reduced and the above steps repeated at reduced gain.
(for example if the measured “own” RSSI is -120dBm and the donor RSSI is -90dBm, set the
RSSI
CAS Threshold
to -110dBm <
RSSI CAS Th
. < -96dBm)
UPLINK MAXIMUM GAIN SETTING:
Ensure that the correct channel is selected (if the OCR is programmed with more than one
channel in the
Channel Data
list).
Set the best RSSI level required (usually -115dBm) in the
RSSI CAS Th ON
field.
Set the power output to the calculated level required to reach the Donor site (allow for at least 6
dB margin).
Key up the OCR by setting
PTT
to ON.
Read the “own”
?RSSI
level from the
Maintenance
screen
