Teleste CXE160, User Manual, Page: 9 / 20

User Manual CXE160
59300393 Rev.001
Broadband Cable Networks August 31, 2009 10(20)
10
Adjustments
Forward path
Set the downstream slope of the amplifier according to the network plan
calculation by means of the mid stage slope selection jumper (Figure 4 pos. 5).
The available options are “flat” or “8 dB sloped”.
The output level of the amplifier is adjusted with the variable input attenuator
(Figure 4 pos. 3). Measurements on the output are made at the -20 dB output
test point (Figure 4 pos. 8). Make final adjustment of the output slope with the
variable input equaliser (Figure 4 pos. 4).
If you are having trouble obtaining the expected output level then check the
input test point (Figure 4 pos. 2) to verify that the level is as expected at the
input of the amplifier. The mid stage gain selection jumper (Figure 4 pos. 6) can
be used to reduce gain with 8 dB if input levels are enough to cause a high
distortion level in the input amplifier.
Return path
The return path adjustment is based on unity gain principle such that the return
path gain of the amplifier exactly matches the loss of the cable following it (i.e.
cable span toward the headend). Connect measuring equipment where the
return path ends (normally at the Head End, HE or at Hub). Start adjustment
with the first amplifier nearest to the headend.
The return path requires a specific signal level for proper operation. The ideal
level at the amplifier is based on the incoming power and the maximum loss
through which that signal must travel on its way to the amplifier. A typical
channel level at the return path input is in range of 60…75 dBµV .
Inject a test signal of known power to the output test point (Figure 4 pos. 8). The
output test point can be used as an injection point for return path test signal.
Measure the output level at the headend. Adjust the gain (Figure 4 pos. 12) and
the slope (Figure 4 pos. 10) of the amplifier until the target level is produced.
Maximum control range for the return path slope is 9 dB. The adjustment range
for return path gain is 15 dB. In the case of high input level it is recommended
that the return path input attenuator is in -10 dB mode. (Figure 4 pos. 9). Thus,
it is possible to achieve higher attenuation with a maximum amount of 25 dB.