10T and number of twists per foot.

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3 total messages Started by Steven Lendt Thu, 21 Jan 1993 21:37

#1015

Author: Steven Lendt
Date: Thu, 21 Jan 1993 21:37

14 lines
1332 bytes

How many twists per foot in solid core unshelded twisted pair wire are
needed to make it live up to level 3 10baseT spec?
Also, how many punch blocks (old 66 type) is it safe to go through if the 
total wire length is not greater than 75 meters?

Thanks in advance!
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Re: 10T and number of twists per foot.

#1037

Author: Dan Pike
Date: Sun, 24 Jan 1993 22:45

15 lines
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In article <slendt.105.727652267@unomaha.edu> Steven Lendt,
slendt@unomaha.edu writes:
>How many twists per foot in solid core unshelded twisted pair wire are
>needed to make it live up to level 3 10baseT spec?
>Also, how many punch blocks (old 66 type) is it safe to go through if
the 
>total wire length is not greater than 75 meters?

I'm pretty sure the recommended number of twists per foot is 7tpf.  As
far as the punch block question goes, when I was working at Apple we
figured out that each punch on a 66 block added the equivalent of about
20 feet of cabling.  This wasn't any scientific testing though.  I think
we measured it with a TDR.

-Dan

Re: 10T and number of twists per foot.

#1068

Author: tanemeth
Date: Wed, 27 Jan 1993 23:40

16 lines
1287 bytes

In article <slendt.105.727652267@unomaha.edu>, slendt@unomaha.edu (Steven Lendt) writes:
> How many twists per foot in solid core unshelded twisted pair wire are
> needed to make it live up to level 3 10baseT spec?

EIA568 spec. says "7 to 10 twists per foot".  Most cables I have seen interpret
this as 7 for pair 1 (blue), 8 for pair 2 (orange), 9 for pair 3 (green) and
10 for pair 4 (brown).

> Also, how many punch blocks (old 66 type) is it safe to go through if the
> total wire length is not greater than 75 meters?

Always as FEW AS POSSIBLE.  Should ideally be 3 max.  From memory, you need to
deduct 2m from max usable length for each extra cross-connect.

Tom Nemeth

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