[Lowfer] Cat 5 cable

Fri, 2 May 2003 15:53:52 -0400

Bob,

You are dating yourself!!!  :>)  I'll bet there is a BSP pn the topic
somewhere buried in our library.

Lets talk about KS numbers and CILI codes.   Only kidding.

The frame at one of the Hartford CT  CO's is around 200' long with literaly
thousands of voice line, DSL lines all laying side by side for

Also think abut the multi-hundred pair cables that run for miles parallel to
and only a few feet from 23 and 40 KV lines.

No crosstalk  or very little.

This is my second year using cat 5 to the LF antenna "range"

I won't go back

"they can have my Cat 5 cable when the pry from my cold dead fingers"

PauLC
W1VLF

Cat 6 is here now too........  Yehah!!

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of [email protected]
Sent: Friday, May 02, 2003 3:00 PM
To: [email protected]
Subject: Re: [Lowfer] Cat 5 cable

The twisting together of numerous pairs is a whole science unto
> itself. Paul or
> one of his Telco guys will have to fill us in on that!
>

Actually think cross talk

the biggest problem , so they say in converting to cable from open wire
back in the dark ages
was keeping signals in the same cable bundle from interfering with each
other .
If anyone remembers open wire then you should remember the transitions
that happened every 5000
feet or so where one side of the wire was crossed over the other. This
was to balance the line and help eliminate noise and cross talk on the
long runs from adjacent open wire lines from the central office. The same
thing holds true for the cat. wire. It is twisted to provide a standard
impedance and make it less influenced from the environment it is used in.
In the wiring frame in a Central office where the outside plant was cross
connected to the inside equipment the frame jumpers were also twisted.
This was to be sure a jumper wire that may have several hundred volts of
B+ and data on it did not interfere with the conversation going on in the
wire next to it.

I have some JPGs of what this looks like

I still dont understand how an unshielded ,twisted pair can provide
better isolation than a piece of coax.
but remember the frequencies involver are relatively low. The important
factor appears to be isolation
and a balanced twisted pair will do a better job than a shielded un
balanced coax

We find that in general a balanced loop works better than one that is non
balanced. The problem isnt loss as much as its isolation and balance

I think !

FYI

it used to take a half day to align up an amplified voice circuit. The
problem was to minimize the return loss so the 2 wire to 4 wire thing
wouldnt sing ( feed back ). Remember a long talk path has to have
amplification in both directions .This could be a real problem to get the
circuit ( ca. Pr. ) to be flat from 300 to 3000 cycles within 1.5 Db.
Often you couldnt do it and the outside plant people would have to look
for bridged taps which were side extensions from the pair you wanted to
use which were probably un documented and placed years before and didnt
cause a problem, just until you wanted to use it for a circuit.

To get that last 1/5 Db of flatness could be a real challenge.

Today they plug the equipment in/on to the ca pr.. push a button and the
amp does it all within seconds
and unless the facility ( ca pr ) is bad it can be turned up for service

Today the computer switches which convert your voice into a Digital ( PCM
) signal is flat ,, FLAT
within 300 to 3000 Cps. Through the switch at 3000 cycles there will be 0
Db loss .  However at 3100 cycles
the loss will be 30 + Db. With a Step by Step mechanical office, 900 Baud
was a fast rate exchange

Ah the smell of watch oil and bank cleaning fluid   HAR

Bob  K3DJC

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