User Manual
CXE180
59300401
Rev.001
26.5.2010
11(12)
Upstream signal path
Optional return path operation needs plug-in diplex filters (Figure 4 pos. 3 and
9).The available diplex filter types are CXF030 (30/47 MHz), CXF042 (42/54
MHz), CXF050 (50/70 MHz), CXF065 (65/85 MHz) and CXF085 (85/108 MHz).
It is also possible to use special diplex filter of type CXF065 18 in the output
diplex filter plug-in (Figure 4 pos. 9). CXF065 18 is a combined diplex filter and
ingress blocker. It blocks out the lowest frequency band (5…18 MHz). If return
path is not used at all, diplex filters can be replaced by forward path jumpers
CXF000.
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 upstream signal 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. 10).
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.
16) and the slope (Figure 4 pos. 15) of the amplifier until the target level is
produced. Maximum control range for the return path slope is 15 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. 14). Thus, it is possible to achieve higher attenuation with a maximum
amount of 25 dB.
