User Manual

AS4000 Release3 and Release 4 Central
Terminal Installation and Commissioning
DLP-017
605-0000-432
Issue 1.3a Date 18th October 1999
Page 3 of 6
e) The single user output is 18dbm. The TX output power level is maintained by a
power control loop in the system. For the power loop to work the CT RF card needs
to generate greater than +21.75dBm, this condition can be achieved by using the
Sitespan to set four users in service without any STs in operation. This forces the
four modems (i.e. two modem cards) to stay in the high power acquisition mode.
Four users provide an output of 24.26 +/- 1.0dBm.
f) For the CT to reach its nominal output power from zero using the control loop
would take a considerable length of time. To bypass this process, the power control
loop may be overridden using the Sitespan to set the TX power the control voltage.
g) Using the Sitespan select the RF Card view from the Shelf view.
h) Set the transmitter volts to 2.2 volts by using the Up/Down button. Observe that the
auto levelling sets the Output power to 24.26 +/- 1.0dBm.
i) Record results
j) Switch off rack. by placing both breakers in the off position.
k) Ensure that the power Output is at steady level before setting up the RX gain
control.
13. Connecting Test CRU
The purpose of this test is to enable the RX sensitivity to be set to -98dBm to
within 1dB. This section provides details of the test set-up for the setting of
the RX gain control.
a) Switch rack off by placing both breakers in the off position.
b) Disconnect terminations on DIP/LNA1 and TX filter.
c) Connect the cables and accessories to the CT rack for Modem Shelf setting
up and functionality testing as detailed below. Set the 0-11dB variable
attenuator to a nominal 5dB (the insertion loss of the test circuit should be
106dB between point A and B.
Note: If the TX Filter is fitted terminate the TX 3/4 as shown in Figure 45.
d) Switch the power back on at the breakers.