HF Transmitter #09 - Directional Coupler, LPF & Antenna Relay

Immediately downstream of the final power amp, I'm adding a LPF (low pass filter), a directional coupler, and an antenna relay - all on a common printed circuit board. The directional coupler will allow me to measure forward and reflected RF power, so that I can calculate in the Arduino software the transmitted power and the standing wave ratio (SWR). No endorsement is made nor implied to any commercial products referenced in this episode.