007,
radial number/length/diameter /proximity to monopole directly effect monople resonant frequency,
shockwave,
did you have nec set to show currents in their correct phase and magnitude when it indicated out of phase radiation near the tip?
from what i have seen the upper 1/2wave always assumes a sinusoidal current distribution with maximum voltage at the tip and imax 1/4wave down from the tip,
i do think that extending too far will cause high angle lobes to apear as seen in open sleeve antennas with monopole to sleeve ratios in excess of about 3.2:1 using equal diameter elements,
imho this could be why we both see a drop in performance as we extend towards the vectors original length and beyond,
taking all the vectors variables into account id say its impossible to guess the electrical length from physical measurements of length,
id also guess that it won't be much past .8wave before we see high angle lobes starting to form when using 1/4wave radials,
other length radials may change the situation,
the whole antenna needs more experimentation ,
we understand the sigma in principle but i don't think we understand the effects of relative element length adjustments with the gamma fed version,
the effects of the hoop and the question of isolation and choking also need looking at in more detail,
then we can start looking at what the astroplane is
