[conspire] RS-232-C (was: Re: DE-9, not DB-9 (was: conspire list hacked?))

[paulz at ieee.org]

 There were more changes than just the plastic.  CAT5 and earlier used #24 wires.  CAT6 uses #23, slightly larger.  The LAN cable industry has grown big enough to be able to demand a "non-standard" wire size.  

I don't know exactly why the change, but it would increase the capacitance to offset the change in dielectric.  

Some years ago, I was looking to buy a bunch of cable for TV.   Fry's had cable in lengths from 3 ft to 30 ft.  The larger lengths had slightly fatter center wires.  My educated guess was that short lengths had higher dielectric constant.  Or they were considering that loss per foot was more important for longer wires.
I had considered buying an assortment of lengths ready made.  Instead I bought a big spool of good cable and a crimping tool.
Paul

    On Saturday, March 9, 2019, 12:46:11 AM PST, Michael Paoli <Michael.Paoli at cal.berkeley.edu> wrote:  
 
 > From: Texx <texxgadget at gmail.com>
> Subject: Re: [conspire] RS-232-C (was: Re: DE-9, not DB-9 (was:  
> conspire list hacked?))
> Date: Fri, 8 Mar 2019 19:41:26 -0800

> Improvements in cable enabled pushing the RS232 standard.
> When you look at those twisted wire pairs, you are looking at the magic.
> The specs of the cable depend on the number of twists per foot and the
> insurance that the spacing between
> the surfaces of the wires inside the insulation remaining fairly constant.
> This is the difference between the various "CAT" numbers.

There's more to it than just that.  The types of materials use also
matter a lot.  Most notably the dielectric properties vary.
Low-capacitance ("lo cap") cabling uses significantly different
insulation around the conductors - even if everything else about
the conductors is the same.  Think of a simple basic
capacitor - a pair of metal plates.  Change nothing else but
what insulating materials are placed between those plates,
and the capacitance of that capacitor can be changed quite radically ...
well, same deal with the cabling - change the insulating materials
and the capacitance between conductors can be changed quite substantially.

> People who think they know everything annoy the hell out of those of us who
> DO!

Nobody knows everything.


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