I'm currently working on protecting 1000Base-T Ethernet lines from EMP using filter connectors such as described on page A-7 of this doc:
http://www.glenair.com/catalogs/mil_dtl_38999_cylindrical_connectors.pdf
One manufacturer can provide a minimum capacitance of 30 pF from each connector pin (TX+,TX-,RX+,RX-) to the connector shell which is connected to chassis.
I'd just like to know if anyone sees any trouble here? I don't think they'll load down the signal since they're connected to chassis and not across the lines.
But I might be wrong. Thanks.
Best Answer
An Cat. 5e UTP has 3 pF/m, or 300 pF / 100 m. Using this filter (like any other) you decrease the possible link budget, but this is the cost of protection. Why not? Or is it so hard for your application? Compare with 50-60 pF/m for S-STP.
Also, Ethernet has 100R at both sides in parallel, resulting in 50R equivalently. Both sides protection Tau = R*C = 50*2*30E-12=3E-9, i.e. 1/Tau is about 333.3(3) MHz, therefore it does not (significantly) limit the connection.