Server NIC (UTP) to coax hub connction?

A Compaq Proliant ML370G2 should be connected to an existing network with an 8-segment coax hub that links some 70 PC’s. With a media converter from UTP to coax to connect the server to this hub, this does not work. Clients do not see
the server. Of course I know I should have changed the network from coax to Cat5. We hope to do that next year.
What is missing? A second NIC in the server with a fixed 10Mb speed? or a
switch AND a media converter so that the clients and server use 10Mb only?