"greg mushial" wrote in message
...
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.

The main difference is the interaction between the antenna and the ground in
forming the lobes. Ground mounted vertical will have one fat lobe, as you
start increasing the height the lobes will start splitting, more of them,
with different magnitudes. Also "looking" out for the ground for reflections
further out.
Using demo version of EZNEC and modeling it will demonstrate the effect.

73 Yuri, www.K3BU.us