FreeLists / si-list / [SI-LIST] Re: Metallic Transmission (UTP modelling)

[john <johndp@xxxxxxxx>]

Chris,

Figure 8.2 page 464 is based on the EIA568B specification, and are the 
worst case values
for a CAT5E cable, this corresponds to the data from Addison cables :-

http://www.addison-tech.com/Addison%20Product%20Specification%20Download/English%20Version/Lan%20Cable/UTP%20CAT5E%20CABLE.pdf

Cat 5E cable has Zo(min) = 85 Ohms (100Ohms +/- 15) so  3.115 yeilds
 
Loss =  19.2dB/100m

add in the DC loss (0.17Ohms/m) and dielectric losses and you'll be in 
the right ball park

Regards

John

Chris Chalmers wrote:

>Si List,
>    I have been trying to calculate the attenuation in the skin effect
> loss region of a piece of CAT 5E cable operating at 100MHz however
>I am not happy with the answer I am getting.  I am working from Dr Johnson's
>High
> speed Signal Propagation Book.  I am not sure whether I am
> applying the formula correctly.
>
>     I have tried to take the example in the HSSP book to ,
>   calulate the attenuation ( in the skin effect region) at 100MHz for Cat
>5E cable.
>
>      taking Ro = 1.189ohms/m  24 AWG    from formula on page 461
>      and wo  = 10MHz
>
>  attenuation  in skin effect region  from page 192
>
>  attenuation db/m = 4.34 (Ro/Zo) * SQRT(w/wo)    (equation Equation 3.115)
>
>                           = 4.34 (1.189/100) * SQRT ( (2x PI x 100000000)/
>2 x PI 10000000)
>                           = 4.34 (0.01189) *  3.1623
>                           = 0.163  db/m
>
>  From the graph on page 464 for cat 5E, the attenuation looks like
>22db/100m
>  not  16.3 db/100m like I have calculated.
>
>   The example in the book works out the values Ro and Wo for Cat 3 cable
>but I
>   can't see how the terms in it could be any different for Cat 5E cable
>since the
>   terms in it are mostly to do with the AWG of the wire.
>
>  I am possibly being very silly here but any help you can provide me with
>   would help loads.
>
>  For those of you who don't have this excellent book, a sample chapter of
>this
>   book is available at http://www.phptr.com/articles/article.asp?p=101149.
>   Well worth buying!
>
>  Best Regards
>
>  Chris
>
>
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