On Saturday, February 15, 2014 11:39:51 AM UTC-6, Jeff Liebermann wrote:
I haven't
seen any high VSWR 5/8 wave antennas, so it's not VSWR.

Actually, a 5/8WL antenna is a standing wave antenna. Therefore, there is a standing wave *on the antenna element* no matter what the feedpoint impedance. The SWR on the loading coil will be higher than the SWR on the antenna element. All that a resistive feedpoint on a standing wave antenna means is that the forward wave *on the antenna element* is in phase with the reflected wave *on the antenna element* at the antenna feedpoint.
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73, Cecil, w5dxp.com