Naively, it seems like using an autocoupler at the base of a reasonably long vertical radiator (call it 43 feet - roughly 5/8 wave on 20m) should work OK for frequencies below the point where numerous lobes start appearing and much more of the radiation goes upwards. It seems like a 43 foot vertical might be ok up to around 18 MHz by that logic, but maybe not so good for 15 or 10m (?). Comparing such an antenna with a fan-vertical type, like the DX commander, where I think the resonant wires are all quarter wave for 40m - 10m (apart from the 15m band which uses the 40m element as a 3/4 wave), assuming the ground radial systems are the same for both, would one expect about the same performance? I guess the 5/8 wave on 20m would outperform the quarter wave case... how about 30m and 40m? Seems like the fan vertical could take the full legal limit, but maybe a high power autocoupler could be pricey. The question pertains to 18MHz on down as a fair comparison. People can fool themselves into thinking all is well when the tuner in the shack shows a 1:1 SWR, as we know (little power might be getting to the antenna), but can we also fool ourselves with autocouplers at the antenna end of the transmission line? In other words is a non-resonant vertical with an auto-coupler at the base "just as good" as a resonant vertical?