# Test of 10base2 ethernet LAN setup

Discussion in 'General Electronics Chat' started by irastha, Apr 15, 2009.

1. ### irastha Thread Starter New Member

Mar 6, 2009
5
0
Dear friends,
I read some simple test in the article http://webdevelopersjournal.com/columns/greg3.html. It goes like this...
"What do you do when something goes wrong? Get out your little multimeter and test the cable. From any T-connector, you should read 27 +/- 5 ohms; from any end of the cable, remove one of the terminators, and you should read 55 +/- 10 ohms. Remove BOTH the terminators, and you should read open circuitinfinity ohms! If you get these readings, your cable is probably A-OK. If not, track it down".
I did this test with my setup. It seems ok. But I cannot find an explanation to why we should read 27 +/- 5 ohms at each T connector.
I would really appreciate any hint from any one.

irastha

2. ### Wendy Moderator

Mar 24, 2008
21,838
3,047
Because the two 50Ω terminations are parallel, and will be half their normal resistance. The extra ohms mentioned are the cable wires resistance. I still have my old 10Base2 working, along side my 10BaseT and my wireless. My network evolved, it wasn't planned per se.

3. ### irastha Thread Starter New Member

Mar 6, 2009
5
0
Thanks. I also guessed so but I am confused at some points.
I have this kind of setup for example.
50(t)-T--------------T---------------T-50(t)
l l l
220ohm 220ohm 220ohm

where --------coax cable (50 ohm)
T=T connector
50(t)= 50 ohm terminator.

I want to electrically see the behaviour of this setup. I did the measurement by giving input at the first node and measured voltage at second and third node. But I am not able to understand the behaviour of the circuit.
Can anybody think of the equivalent circuit of this setup.
i mean, if we want to draw the equivalent circuit of this setup. Should we replace the cable by 50 ohm resistance in series or parallel or something else?
I know its different task than a regular 10base2 ethernet, but I need to find this out for my work.