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

["Chris Chalmers" <cchalmers@xxxxxxxxxxx>]

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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