How to build, convert and use duplexers, and antennas in ham radio.  Practical knowledge, not theory will be the goal of this study group.  Math and theory are useful, but in these areas the reality is that one almost never has the ideal components or physical environment that a simulation or model depends on, so most of duplexer and antenna building is an art, rather than a science.  But test equipment and measurements are key to sucess.