Been out of ham radio since the '60's (raising a family etc) and am
slowly coming back (though given the noise I see in r.r.a.misc I
wonder if I really want to :-( ).

My question is one of trying to understand propagation - with a ground
mounted vertical, if I remember correctly, one treats it as if it's a
half wave dipole, where one leg is above ground and the other is
virtual and is a "ground reflection", hence the importance of good
ground/radials etc. I assume if I had a balloon up several thousands
of feet and dropped a half wave dipole (still center fed, but hung
from one end), then it would behave like a ground based horizontal
dipole, other than being polarized vertically (ie, no virtual / ground
reflection for the lower half). The question is: when does one make
the transition btwn the two modes, how far off the ground (in terms of
wavelengths)? If a vertical dipole is 10 wavelengths above the ground,
does one still have to consider the ground as part of the antenna? how
about 2 wavelengths? If someone could walk me through a thought
experiment on this I'd appreciate it.

thanks,
greg

ps. yes I've Googled this and found nothing, likewise have and read
ARRL big antenna book + several of their long wire books, likewise, no
mention.