Ethernet transformer core material

Red tape wound?

Think about it. Gigabit ethernet works at 125MHz clock rate. Powdered or tape wound iron isn't going to work much over perhaps 100KHz. That leaves ferrite.

I'm not sure of the exact core material type. I think it's Mn-Zn based:

but I'm not sure.

If you're curious, find an old ethernet card with a transformer, and crack it open. (Learn By Destroying).

Thanks I forgot to metion its for 10base-T

TDK articles on LAN magentics:

Ferrite core characteristics:

Some photos of what's inside:

For data sheets:

It took a while to contrive the proper search term. Search Google for "ethernet magnetics" or "LAN magentics".

thanks!!!

Of course they are ferrite, for high mu for the flux-coupled transformer, but I don't know why you'd say that powdered iron wouldn't work over ~100kHz. Certainly powdered iron is used for inductor cores at tens of MHz, and yields higher Q and generally better inductance stability at those frequencies than any ferrites I'm aware of.

Cheers, Tom