Likewise, I concur with Agent86.
You need to have T-pieces and terminators to get coax to work. Also, there is a minimum distance between connected nodes -- it's such a long time since I worked with large-scale coax installations that I cannot remember exaclty what it is, but if you've got a metre or two between the two boxes that should be OK. Some early cards do not autoselect the media, so you might have to set a jumper on the card...