CATV Network Design Calculations FREE cabling and networking Helpdesk
 Question by D. Adelman posted 26 Oct 2004
 CATV Network Design Calculations
I am in the process of proposing a CATV system and am having some difficulties determining the proper equipment to propose. Here's the situation:
I am running one RG-11 backbone to a distribution closet(DC) on each of 5 floors in a building. From each DC I will need to split/tap off and continue down the corridor on each floor tapping at certain points and running RG-6 into each room.

Let's look at the 1st floor only...My 1st DC is ~260' from the headend. In the DC I will split the RG-11 with one cable going east and one going west. The "eastward" will run 50' to an 8 port tap and stop at which point I will run RG-6 to each of 8 TV's. The "westward" will run 15' to the first 8 port tap (spliting of all 8 to TV's) then continuing on to a 4 port tap 50' past the previous tap (splitting of all 4 to TV's here as well) then continuing another 50' to an 8 port tap, then another 50' to a 2 port tap.

The specs of the project are:
-The forward frequency response must be at 49-750MHz w/ +3 to +10dBmV @ each TV outlet.
-The return response must be 5 to 35 MHz
-The system must be able to deliver 5 to 10 dBmV return level at 5-35 MHz to the headend w/ a 38dBmV reference from a typical room location.
-I beleive my max output is 42dBmV at the headend

My question (finally) is:
-What type/size taps to use/how to calculate?
-Do I need amlifaction on the system and if so where?

 Answer by Dmitri Abaimov posted 27 Oct 2004
Dear D.,

That was a very detailed request, sorry I cannot reply with equally detailed response within the scope of a helpdesk answer. However I will be glad to help be giving you some pointers.

The way a task like yours is normally handled is this: you contact a CATV manufacturer, such as Blonder Tongue (just to give you an example, others do that too) and tell them that you are considering using their product in the system you are designing. They will be glad to assign a design engineer to you and he will get all the details from you (make sure you save all the details of this message or just send him to this page) and come up with a specification that includes this company's components configured in the best way. We've done that multiple times, and it makes your design job easier, bill of materials more accurate, and generally everybody's happy.

Good luck!

Dmitri Abaimov, RCDD

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