Reading up on how to calculate cable lengths as a follow-up to my previous question, I understand that you have to use (102-H)/(1+D) to calculated the stranded length (C) and H+C to calculate the channel length. And that the channel's max length is 100m (in my example for 1000BASE-T).
Using the standard for D which is 0.2 (for 24AWG UTP) and 90m horizontal get me C=10. Does this mean that 22AWG cables (D=0.2) will always be out of specs (since the channel lengh will be 102 regardless of the size of the horizontal length)?
Where I'm also uncertain, but I can post that into a separate questions if needed is this example:
For example, if using 60 meters of horizontal solid category 6A cable and 40 meters of stranded 24 AWG category 6A patch cable with a 0.2 de-rating factor, the total length of the channel must be reduced to 97.5 meters
How exactly would I reduce the cable? If horizontal link is permanent an can not be change I have to reduce to 37,5m stranded in order to get to 97.5?
And the last question is, what's physically behind the math/specs? Why can't I use more then 90m in my first example? With 91m horizontal I get 9.2 stranded and 100.2 for the channel length. Even if reduce the stranded to to almost zero I'm out of specs... I just can't warp my head around this. I just want to select "the right patch cable" in an existing setup (in an office building)... and thought it would be a good idea to know a bit about the limits. But this whole approach seems to be a bit complicated or did I just start out to naive?!