Greetings Joe50,
You may not find it documented anywhere so let me add this to your epuation,
In the Head-End, at the point of signal insertion, many have used splitters, effectively. However the HFC project I recently completed we found that it was necessary to use a DC passive for interjection, I don't think it made a difference from an 8dB, to a 16dB. There was a problem with the use of splitters.
Wish the best to you....Petergunn
