When you are dealing with cable modem service and return path there are many things to consider, and many factors that can effect the transmit power. Your optimal input to a cable modem is 0db, The cable modem is auto throttling and will throttle up to the level it needs for the CMTS to receive 0db back at the headend. Things that can effect this are to high of a forward path to the modem that requires to much padding at the modem for the return to operate properly. An improperly balanced return path that causes to much attenuation in the return path causing the modem to throttle up to provide 0db the the CMTS or improper combining and padding in the headend to the CMTS causing to much attenuation causing the modem to throttle up. In some cases you may be required to install a house amp at a home, If the house amp only amplifies the forward and not the return this can cause to much attenuation in the return path.
The bottom line is if you are achieving the proper levels at the input to the modem and the modem is throttling up to high you have a plant related issue not an install issue. It can be caused by many things but in the end it is a system related issue. Now on the other hand if you start going below 0db into the modem you are increasing the attenuation to the modem and causing the modem to throttle up higher. Lets say that your system is designed to have 0db to the modem and with the system balanced for unity gain on the return to cause the modem to run at 45db to 50db Output on the return to provide 0db at the CMTS, and you have -10db at the modem on your install you are now causing the modem to throttle up to 55db to 60db to achieve 0db at the CMTS and you have a bad install.
Re: voip/hsd
Member #: 29777
Registered: 3/28/2004
Posted:
307
Name:
DJ
Company:
Multi Cable Inc
Occupation:
Operations Manager
Location:
California
Personal:
Experience:
~40 years
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