802.3 signal levels

Sep 28, 2006 3 Replies
D

Can someone point me to documentation that explains the signal waveforms seen on 10BaseTX and 100BaseT cables? I've read the IEEE standard, but am having a hard time getting a complete understanding from that document alone. A couple very basic questions...


1.) What are the max voltage levels for each speed?
2.) What is the max frequency for each speed?

I've read that the max frequency for 100BaseT is 31.25MHz, but I have measured 62.5MHz. How can this be explained?



Thanks, David


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D

I found voltage specs. for 10BaseTX. It is 2.2V to 2.8V for all data and -3.1V to +3.1V for link pulses. I am still searching for 100BaseT numbers.

I still don't understand why I am seeing 62.5MHz. Any help with this would be greatly appreciated.

Thanks, David

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M

What are you measuring it with? A spectrum analyzer would show you all the signals involved.

Service to my country? Been there, Done that, and I\'ve got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida
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D

I measured it with a scope. I expect that it is normal, but I don't understand ethernet well enough to know why. One source of information claims that the max. frequency is 31.25MHz, but I clearly measured double that.

Thanks, David

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