max length of RS-232 network link?

Chad Kurszewski
Wed, 12 Jul 1995 07:33:47 -0500

> >4. Ultimately, you could go with optical fiber on the RS-232 links.
> >   It's expensive, but it works. Talk to Rich, K5NA, who has done it.
> Probably a cheaper alternative to item 4 would be to use an RS422 converter
> at each computer.  If I remember right it requires a 2 pairs of wires (ie. 
> telephone "twisted pair" cable), and it turns the unbalanced signalling of
> RS232 into 2 pairs of balanced lines which are much less susceptible to
> interference and it'll go a couple thousand feet.  This'll be a LOT cheaper
> than fiber... and you could still work it into a loop configuration easily.

If you look into this route, you may also want to check out the
RS-488 converter boxes.  If I recall correctly, they convert RS232 RX
and TX into ONE twisted pair.

The benefits of RS-488 (and I assume RS-422) is that they use a
differential voltage to determine states, whereas the RS-232 uses
actual voltage level.  So, for long runs, the IR losses in the RS-232
lines can screw up the levels.  As for RS-488, the IR losses can be
great and you still would have a voltage differential which would still
convert correctly.

If I recall, the boxes go for around $100.  All in all, probably cheaper
than optical fiber cable and converters, and not that much more expensive
than running two lines of RG-58 to each computer.

Chad Kurszewski, WE9V                   e-mail:
Sultans of Shwing       Loud is Cool....yeah, heh, heh, heh, LOUD IS COOL!!!

Administrative requests: