Re: Shielding of CAT 6 cables (was Re: [tlug] FTTH ISP recommendation)

[Edward Middleton <emiddleton@example.com>]

jep200404 wrote:
> Edward Middleton wrote:
>   
> > My point was that standard phone cables unlike category 6 cable wasn't 
> > designed for high bandwidth applications and so is not going to have 
> > adequate shielding. 
> >     
>
> What's the relationship between bandwidth and shielding? 
>   

Shielding causes decreased noise or increased Signal to Noise Ratio 
SNR.  For the relationship between SNR, bandwidth and channel capacity, 
from wikipedia[1]

   C = B log_2(1 +(S/N))

   C is the channel capacity in bits per second;
   B is the bandwidth of the channel in hertz;
   S is the total signal power over the bandwidth, measured in watt or
   volt2;
   N is the total noise power over the bandwidth, measured in watt or
   volt2; and


If you have a lower bandwidth cable B, like a phone cable, you need a 
higher signal to noise ratio S/N to gain the same channel capacity.

> How much shielding does the CAT 6 standard require a CAT 6 cable to have? 
>   

Good point, Category 6 UTP obviously has none, but it has greater 
bandwidth so can sustain higher channel capacity under lower SNR.

Edward

1. http://en.wikipedia.org/wiki/Shannon-Hartley_theorem