[SI-LIST] : Ethernet RJ-45 connectors

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From: Jan Vercammen ([email protected])
Date: Wed Jul 05 2000 - 00:49:08 PDT


I have signal integrity - EMC questions concerning Ethernet RJ-45 connectors.
I have done some browsing on dimensions of these RJ-45 connectors and I have
found that they seem to come in two sizes: a smaller one with a body length
of 19.2mm and height of 12.2mm and a larger one which is about 21.3mm of length
and 13.6mm high. The width of 16mm of the connectors is about the same for both

It seems that the larger type is a category 5, the smaller one does not seem
to comply with cat. 5 as one can gauge from the AMP web site.

Currently we use the smaller type, which is likely non category 5. Our hardware is
designed for 100Mbit twisted pair. I have looked at two other Ethernet 100Mbit designs
(in new PC and in a Sun workstation) and I have found the smaller sizes.

These are my questions:

-1- how critical is the RJ-45 connector in 100Mbit Ethernet data transmission? Is it
    required to use category 5 connectors or is this not important?
-2- Am I correct to associate the larger sized RJ-45 with category 5? What is different
    in their mechanical design? Spacing between the connector pins to control connector
    crosstalk and signal integrity?
-3- Is there a difference in EMC performance of both sizes? Does a category 5 connector
    radiates less than a non-category 5, so to speak!
-4- one category 5 RJ-45 connector drawing carried the following statement: "jack
    cavitiy conforms to FCC rules and regulations, part 68 subpart F". I assume that
    this is related to safety and isolation voltages?

Thank you for your time.


Jan vercammen
EMC/PCB engineering Agfa-Gevaert NV, Belgium

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