Harold,

I have an old 8 port hub. It hasn't been used in 15 or 20
years but seems to still work. I would be glad to send it to
someone who could use it. Send me a mailing address offline.
The 5v 800ma power supply weighs a ton so I would prefer to
not send that.

Allen

-----Original Message-----
From: piclist-bounces@mit.edu
[mailto:piclist-bounces@mit.edu] On Behalf Of Harold
Hallikainen
Sent: Thursday, August 30, 2018 12:50 AM
To: Pic List
Subject: [EE] Passive Ethernet Hub?

I have a hub here that I use all the time with Wire Shark.
Sometimes I
need to help someone debug something in the field, and they
don't have a
hub, and they are getting hard to come by.

Since 10/100 Ethernet uses two pair, one for transmit, and
one for
receive, it SEEMS like it should be possible to make a
resistive hub where
each transmit pair drives the receive pairs of the other two
ports (total
of 3 ports). I've done similar resistive networks for audio
splitting
while maintaining impedances. But, I haven't figured out
whether this
would work or what the resistor values would be. I did find
a passive hub
using a bunch of diodes, but it seems like resistors should
work. I also
see Ethernet taps where there are four ports. Data going one
way between
the other two ports shows up on one of the monitor ports
while data going
the other way shows up on the other monitor port. This
requires two
Ethernet ports on the computer running WireShark, which is a
pain.

So, any ideas on this? Is it possible to use resistive
splitters to make a
passive hub?

Thanks!

Harold


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