Using a NanoVNA to measure the efficiency of an End Fed Half Wave Transformer

Hello - the is Ariel NY4G this time going into a deeper dive on how a NanoVNA can be used to measure the efficiency of an end fed half wave transformer. End Fed Half Wave (EFHW) antennas have certainly become popular. One thing that is not well understood nor documented is whether one of these autotransformers used in these popular antennas is wasting power that we can begin to care about. An explanation of how to compute this efficiency is explained based on the measured S parameters by the NanoVNA. Two methods are explored - the resistor method and the back to back method. Both these methods ought to give answers in the same ball park. I tend to favor the resistor method because it matches my intuition of how an antenna system is configured. In the end several comparisons are made depicting both iinefficient transformer windings against efficient ones.