>supplier

I don't have one off of my head, because I normally buy off the shelf or
from catalogs. But, by looking at the ethernet card I have in my hands
now, I can see a large DIP transformer hybrid directly connected to the RJ
plug. So practically ALL ethernet cards have a transformer coupled output.

Try to find the exact make of the cards you are using and contact the
manufacturer to know the specs. He will be able to tell you how much their
magnetics insulate. The hybrid on my card is made by Delta (it's a cheap
NE2000 clone card). If the manufacturer does not cooperate, try another. I
am quite sure that they have heard this before.

The ethernet signals for BNC are a very nice rectangular waveform (for a
short network at least) with high = GND and low = -2V (load is about 5
cards). The balanced RJ type of signals are twice that if I'm not wrong.

I seem to remember that some form of dc restoring clamping is required in
hubs or such but the manufacturer will tell you more.

You can also try to contact magnetics manufacturers for ethernet devices
and see what they sell. Maybe they have your 1" transformer ;-)

Peter

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