The article seems to ask how to define a referential term without using reference (i.e. left/right, up/down, clockwise/anti-clockwise, without reference to a static point). Using the example of radio waves, if I wanted to express a basic kind of reference I would start by using pitch (e.g. low pitches to high).

For direction (left vs right), I would broadcast a "beam", increasing in strength on one side, so hopefully an intelligent enough civilization could measure that from "left" to "right" the beam got stronger, perhaps again using pitch to help guide. The problem then would be conveying whether they should follow the broadcast "left to right" or the received "left to right" (i.e. imagine someone holding up their left hand, do they mean your left hand, as in match them, or your right hand, as in mirror them).