This picture should give you an idea on how the return system should be aligned in a HFC. This example is done using the SST and 860DSPi from Trilithic. But it should be the same with the Acterna unit. Some one should tell you the level to introduce at the return input add the lost of the test point and the guy at the HE should set the system for 0 to + 5 dBmV at the CMTS.
