10 Mbps LAN waveforms

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Dec 28, 2006, 1:22:58 PM12/28/06
Hello everyone,
I graduated from college (Electronics Engineering) 8 months ago and
have been working at Larsen and Toubro Embedded Systems and Software
for the past 6 months. During the first few weeks of induction period,
I had the opportunity of exploring the various Test and Measurement
Instrument in our Labs. I started with the Tektronix TPS2024
oscilloscope (200MHz , 2 Gsps, Isolated grounds).
After experimenting around a bit with the oscilloscope, I started
capturing signals which we find in our labs quite frequently...
Telephone, Rs232, I2C etc.. It was real fun to observe these in real
life, specially after just learning about them at college.
It was during this time that I was able to capture the Waveforms of
10Mbps Ethernet.
Well since I dont have any real experience with such kind of things, I
wanted to ask someone who knew all this stuff to tell me if the signals
I captured were correct ones or not?
I am also doubtful of the procedure of capturing the signals

Here is what I did:
I stripped the insulaton of the TX+ and TX- wires in the CAT5 cable
near one end of the cable (the one near the CPU). The other end went
into a 10Mbps Hub.
I used a 200MHz isolated channel oscilloscope to take the measurement
of the differential signal on the TX+ and TX- wires. The Probes were
set to 10X attenuation to keep the bandwidth up till 200 MHz

I tried the same measurement using different setups.
The resultant waveforms are available at:


I have also referred to:
ANSI-IEEE Std 1802.3d-1993 (Conformance Test Methodology for IEEE
Standards for Local and Metropolitan Area Networks)
- Type 10BASE-T Medium Attachment Unit (MAU) Conformance Test
Methodology (Section 6)

According to the waveform given at the start (page 10) of this
document, it seems that what I captured is quite what is required but
still I would like the comments and opinions of others.

I wasnt able to find much regarding waveforms of the ethernet signals
thru gools so I would be happy if you would go through my findings and
post in your comments.

Thanking you

Regards and best wishes for the new year

Anurag Chugh
Larsen and Toubro EmSyS, Mumbai India

Rene Tschaggelar

Dec 28, 2006, 5:38:14 PM12/28/06
u.u...@gmail.com wrote:

Thanks for the wishes.
I'd do the measurement in the way of setup 2 or 3.
The shown waveforms make sense.

Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net


Dec 30, 2006, 2:35:18 AM12/30/06
Just wanted to add one more thing... while I was taking the
measurement, the signal was not getting attenuated.. meaning the link
want affected by the measurement. (that probably means the probes
werent loading the signal..)

Anurag Chugh

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