"Cecil Moore" wrote:
I just modeled a 5.25' long helical using EZNEC at the 270 degree 3rd
harmonic frequency of 26.5 MHz. Both helical and whip are modeled as
lossless. If I understand you correctly, the 270 degree helical ...

A normal-mode helical with a radiating aperture of 5.25' is not a "270
degree" radiator on 26.5 MHz. It is a ~ 51 degree radiator on that
frequency.