ethernet cable?

[Dave Martindale]

If you use anything other than "real ethernet cable", make sure that
the transceiver physically attaches to it correctly before you buy it.
Transceivers tend to bolt directly onto the cable, making their electrical
connection through a drilled hole.  A change in outside diameter of
the cable, thickness of insulation, or diameter of inner conductor could
cause a non-existent or poor connection.  Also, the Ethernet specs say
what the velocity factor and resistive losses of the cable should be to
guarantee that the system will operate properly out to its distance limits.
Either buy cable which is within the specs, or make SURE you understand how
it will affect the network you can build.  Finally, real ethernet cables
have marks on them telling you where to install the transceivers so that
the impedance discontinuities produced by the transceivers produce
reflections which tend to cancel each other rather than adding.  If you
buy cable which isn't marked in this way, measure it for yourself.