User Manual

ADCP-75-114 • Issue 2C • January 2002
Page 18
© 2002, ADC Telecommunications, Inc.
Note: An input signal level of –20 dBm at the DHU produces an output signal level of
+13 dBm (800 MHz) or +16 dBm (1900 MHz) at the DRU. If maximum output is not
required at the DRU, the DHU input signal level may be reduced in order to produce a
lower DRU output signal level. Decreasing the DHU input signal level by 1 dB produces
a corresponding 1 dB drop in the DRU output signal level.
6. Disconnect the power meter from the forward path cable and reconnect cable to DHU RF
IN connector.
FWD LEVEL ADJ
MSB LSB
00
16
2
4
6
8
10
12
14
REV LEVEL ADJ
MSB LSB
00
16
2
4
6
8
10
12
14
INSERT A SMALL SCREWDRIVER INTO THE SLOT.
ROTATE THE SWITCH UNTIL THE WHITE ARROW IS
ALIGNED WITH THE REQUIRED SETTING.
16649-A
Figure 14. Rotary Switch Adjustment
3.4 Reverse Path Level Adjustment
The level of the composite RF signal that should be input to the antenna will vary depending
on the maximum acceptable DRU path loss per the system design. Typically, the design
objective is for the Digivance system to provide a unity gain. Use the following procedure to
adjust the RIU to provide the required reverse path signal level at the antenna:
1. Determine the maximum acceptable DRU path loss per the system design specifications.
2. Determine the total cable loss that is imposed by the reverse path coaxial cable that links
the DHU to the RIU, the coaxial cable that links the RIU to the antenna, and any other
devices (splitters, connectors, etc.) that will impose a loss on the signal.
3. Determine the total gain provided by the DRU antenna and the donor antenna.
4. Calculate the total gain that must be added by the RIU using the following formula:
Reverse Path RIU Gain = [
å System Insertion Loss + Designed Path Loss] – [System
gain (10 dB at 800 MHz, 14 dB at 1900 MHz) +
å Antenna Gain]
The result should be negative which indicates that gain is required.
5. Using a small screwdriver, adjust the REV LEVEL ADJ rotary switches to insert the
gain required as determined in step 4. Refer to Figure 14 for a description of how the
rotary switches work and to Table 4 for the adjustment settings.
Note: The RIU provides a reverse path signal adjustment range of from +28 dB to +59 dB
(for 800 MHz) and +33 dB to +64 dB (for 1900 MHz).