Okay, here is the challenge: what is the most efficient antenna for QRP portable. Why? How? For me, a resonant doublet that has no common mode gets the signal out. This has meant getting the feedline length right. I optimize height for the frequency, 32-33'. What do you say? If you use coax, how do you determine feedline length if you use an antenna analyzer, or, do you use a balun or a 1:1 common mode balun and call it good?