A coaxial physical layer device operates in at least two different modes: a discovery mode and a normal mode. In the discovery mode, a first orthogonal frequency-division multiplexing (OFDM) coaxial signal is received that has a preamble including a plurality of first training fields and at least one second training field. Each first training field is shorter than each second training field. In the normal mode, a second OFDM coaxial signal is received that has a preamble including a single training field. The single training field is shorter than an OFDM symbol.