I am laying out an RS485 driver and read a few design guides which recommend a 120 Ohm termination resistor. This makes sense since the characteristic impedance of twisted pair cables is in the 100 Ohm to 150 Ohm range.
However what confuses me, is how would the signal be affected by the impedance of the PCB? There is also no mention of the connector impedance?
Should I be routing the RS485 traces as short as possible to mitigate transmission line affects on the PCB?
I understand the basics of transmission line theory, however I don't think I fully understand the implications of transmitting between two mediums. Transmission lines make more sense to me when the source and load share a consistent medium.