Defining a 49:1 EFHW Transformer's Losses
End-fed halfwave antennas are so convenient, especially in rapidly deployed setups, and they're easy to build . But how much energy is lost in the 49:1 transformer that makes it possible? Because I operate mainly QRP, and I'm using a rather large core for 5w, I'm not concerned with losses that appear once the transformer's core reaches the Curie temperature. So I can use a nanoVNA, performing a S21 logmag trace on two cores back-to-back, to see how much power my transformer is eating up on the way to the antenna. I used the Fair-Rite 2643625002 core, inspired by excellent results MM0OPX reports in a generously shared spreadsheet of results. Could I get around 0.5 dB loss from 80m all the way to 10m if I used that core in 21:3 turns ratio? My experience with more donut-shaped ones suggested that such broad-banded performance was a tough order: a 14:2 turns ratio works well on one end of the HF band; 21:3 works well on the other. In the end, Colin's accompanying vi